I’ve tried and tested the best rainbow cakes for your kid’s birthday party - and two popular supermarkets stood out above the rest

Here are the best shop-bought rainbow birthday cakes - tried and tested by our Food Editor and her kids...

Table full of the best supermarket rainbow cakes tried and tested by GoodtoKnow's food editor
(Image credit: Future)

From M&S to Tesco, from Sainsbury’s to Morrisons, I have tried and tasted more rainbow cakes than I’d like to admit, and here are my favourites.

The kids' party food ideas have been decided, the goodie bags are packed, and the soft play venue has been booked months in advance - but what about a birthday cake?! If you’re still undecided about which birthday cake to buy your little one for their special day, we (me and my kids, that is) have tried and tested a range of different rainbow cakes from various supermarkets to find the best of the best.

When it comes to choosing the best birthday cakes for kids, my go-to is to make my own birthday cake - be it a rainbow cake from scratch or a DIY caterpillar cake. I really do like baking my own and watching my kids’ faces light up when they see the hard work I’ve put in. However, sometimes there is no time for playing Mary Berry or slaving away in the kitchen for hours and a shopbought cake is the answer.

Being Food Editor on GoodtoKnow for well over 10 years means that I have a wealth of knowledge when it comes to compiling a list of the best birthday cakes and in this roundup, each and every cake has been ordered, sampled, and reviewed by yours truly. Of course, everyone's taste buds are different but I like cake. I like to bake cake, eat cake and I’m a bit of a cake snob (there, I said it) so you can trust that what I’ve chosen is going to be quality and good value for money too as kids' party planning is all about keeping to that budget… she says.

PS... GoodtoKnow's Food Writer has tried and tested the best supermarket caterpillar cakes  for those looking for more kids' birthday cake options

Where to buy the best rainbow cakes and more

Best rainbow birthday cakes - quick list

Best supermarket rainbow birthday cakes

Morrisons Rainbow Celebration Cake

Collage of Morrisons Rainbow Celebration Cake being sliced to reveal rainbow layers

(Image credit: Future)

RRP: £14.50 | Serves: 12-16 | Available: 3 days to collect

The Morrisons Rainbow Celebration Cake certainly got us all talking not just because of the sprinkle-tastic appearance but the raspberry jam filling too as most rainbow cakes we tried opted for vanilla buttercream filling. The raspberry jam added a lovely, fruity taste to the cake, and the sponge itself was moist with a soft, spongey texture. 

When I cut into the layers however I was a little underwhelmed by the colours as they weren’t as bright and vibrant as some of the other cakes, however saying that my kids were delighted to see a green layer, which none of the other cakes had. The buttercream used to coat the cake and hold the sprinkles in place was minimal meaning the cake wasn’t overly sweet, leaving the raspberry jam flavour to dominate in each bite.

My six-year-old said: “I like the jam, it’s tasty. A very good cake and the green layer is very cool. This is my favourite cake. Can I have another slice?”

Morrisons Rainbow Celebration Cake - £14.50 - Morrisons

The BAKERY at ASDA Rainbow Jazzie Cake

A close up of The BAKERY at ASDA Rainbow Jazzie Cake sliced with rainbow layers

(Image credit: Future)

RRP: £14 | Serves: 20 | Available: Online and instore

Asda’s Rainbow Jazzie Cake ticked a lot of boxes for me. Firstly it was big, and certainly a good size for slicing up and adding to party bags - I cut it into 20 ‘squares’ instead of triangular slices and felt like there was plenty of cake to share with this one. 

And at £14, it’s one of the best value-for-money cakes in this taste test. The sponge was light, with subtle vanilla flavour thanks to the buttercream, colourful layers evenly baked, and sprinkles that gave it the ‘wow’ factor. Plus it wasn’t too heavy on the icing either so wasn’t overly sweet. The other thing I liked about this cake is that it’s a great base for those who like to add their own flare as the top could easily be personalised with cake toppers, numbered candles, etc. 

My four-year-old said: “It’s such a big cake covered in so many sprinkles - look at all of them…one, two, three, four, five... 1,074! I love the sprinkles. Wow. The pink layer is my favourite.”

The BAKERY at ASDA Rainbow Jazzie Cake - £14 - Asda

Marks and Spencer Rainbow Layer Cake

Collage of images showing the M&S Rainbow Layer Cake being cut to reveal rainbow layers

(Image credit: Future)

RRP: £16 | Serves: 8 | Available: Online via Ocado

One of the smallest cakes we taste tested, the M&S Rainbow Layer Cake serves 8 which means it's a good choice for smaller birthday parties, or if you’re serving cupcakes, doughnuts, or other sweet treats alongside it. A very neat rainbow cake with defined rainbow layers and colours. 

The buttercream was the highlight for us as it was creamy, smooth, and infused with vanilla, however, it does mean that this cake is extra sweet so brace yourself for the full on sugar rush. M&S also has a bigger rainbow layer cake which serves 12, can be preordered directly on the M&S website, and includes an extra layer of sponge cake too if you need something bigger.

My six-year-old said: “It’s small but I like that it has sprinkles on the side and not on the top, just that swirly pattern. It looks nice and the icing is good.”

M&S Rainbow Layer Cake - £16 - Ocado

Sainsburys Rainbow Layer Cake Taste the Difference

Sainsbury’s Rainbow Layer Cake Taste the Difference being cut to reveal rainbow sponge layers

(Image credit: Future)

RRP: £14.50 | Serves: 10 | Available: Online and instore

There is something homemade about the look of this cake which is a great choice if you want to tell everyone you made it yourself - don’t worry, we all do it now and then. The colours are clear with distinct layers and a fluffy sponge. This cake is a similar size to the M&S Rainbow Layer Cake meaning it's a good choice for smaller, intimate birthday parties. 

This cake is quite heavy on buttercream both on top and layered in the cake, but it does add further flavour to the cake overall - just keep in mind for those who aren’t too keen on buttercream as it might be too much. Priced at £14.50 it’s at the lower end of the budget when it comes to the cost of rainbow layer cakes.

My six-year-old said: “I like the colours inside this cake - the dark purple is very cool and it doesn’t matter that there are no sprinkles on top because there’s more room for candles.”

Sainsbury’s Rainbow Layer Cake Taste the Difference - £14.50 - Sainsbury's

Tesco Rainbow Cake

A collage of images of Tesco Rainbow Cake being sliced to reveal rainbow layers inside

(Image credit: Future)

RRP: £15  | Serves: 16  | Available: Online and instore

Decorated differently from the rest, this rainbow cake by Tesco has a fun homemade vibe with the vibrant blue buttercream which certainly makes it stand out from the crowd. Like the Morrisons cake, this one is also layered with raspberry jam which makes it taste much fruitier and sweeter than the rest.

This cake was quite heavy on the buttercream which I personally wasn’t so keen on as it was very sweet, however, the size, overall look, and moistness of the sponge made up for it. Plus this cake is decorated for you, so you won’t have to add anything extra to make it stand out. The kids liked this one more than me predominately because of the way it was decorated.

My four-year-old said: “I like the rainbow on top - is it chocolate? Can I eat it? The blue icing is good… I’m just going to try some with my finger.”

Tesco Rainbow Cake - £15 - Tesco

Marks and Spencer Under the Rainbow Cake

A collage of images showing M&S Under the Rainbow Cake being cut to reveal rainbow buttercream and vanilla sponge

(Image credit: Future)

RRP: £16  | Serves: 16  | Available: Online via Ocado

Ok, so this is technically not a rainbow layer cake as the sponge itself isn’t rainbow, however, the decoration is and the buttercream inside the cake is rainbow too. Let’s call it a rainbow cake alternative for those of you who want the rainbow look, but not too much of the coloured sponge. 

A really lovely cake from M&S with a light, sweet Madeira sponge, soft buttercream, jam filling, and eye-catching pastel colours. Similar to the Tesco cake, all the decorating has been done for you, all you have to do is add the candles for the birthday kid. This cake certainly has the rainbow ‘wow’ factor when it comes to the overall look - just lacking in the rainbow centre.

My six-year-old said: “I love the colours of this cake and the rainbow and little white bits on top. The icing is clever and the inside with the coloured buttercream is great too.”

M&S Under the Rainbow Cake - £16 - Ocado

How we tested the best rainbow birthday cakes

Three rainbow cakes cut to reveal rainbow layers lined up on a table covered in party decorations

(Image credit: Future)

Before the taste test began, I wanted to make sure that I had rainbow cakes from each supermarket that sold them so it was a case of firstly researching, sourcing, and ordering each cake whether online or shopping in-store.

Once I had all the cakes, I needed to make sure each cake would be assessed with the same criteria so I created taste test sheets marking the price of the cake, how many people it served, where you could buy it (online, instore or both) as well as general appearance, first impressions, flavour, taste, texture, and any other comments on why that cake stood out above the rest, or what made it the best rainbow cake and worthy of being included in this roundup. 

After looking at the decorations, and the size and servings of each cake it was about cutting the cake to reveal the rainbow layers inside, tasting and noting down how even the layers were, what the buttercream looked and tasted like, how sweet or not sweet it wasted, flavour combinations - for example, some had raspberry jam filling others didn’t - and so on.

Then it was time to get the kids involved - which, of course, those of you with kids can imagine was rather chaotic with six rainbow cakes to choose from. However, the children were both very good at trying small pieces of each cake and saying what they liked or didn’t like about it - but most comments from my two were positive. Kids and cake, eh? Then they abandoned ship and had a serious sugar high so we ended up taking them to the park to burn off some energy leaving a massacre of cake crumbs and sprinkles across our kitchen table to deal with when we returned.

Rainbow cake slices on a plate, taste test sheets and testers sampling cake

(Image credit: Future)

What was your favourite rainbow cake?

The cakes in this roundup are in priority order with The BAKERY at ASDA Rainbow Jazzie Cake being our favourite and the Morrisons Rainbow Celebration Cake being a very close second. The M&S Under the Rainbow Cake was a bonus cake I tested as an alternative option which proved popular with myself and my testers too.

What was your least favourite rainbow cake?

Unfortunately, the Sainsbury’s Rainbow Layer Cake Taste the Difference was our second least favourite and despite its vibrant decorations, the Tesco Rainbow Cake was our least favourite.

What’s the best way to cut a rainbow cake?

As rainbow cakes are very sweet it’s probably best to give small thin slices of this type of cake, especially to children as there is a whole lot of sugar in each one. I like to cut my cake into squares, instead of the usual triangles. It’s a great way to stop waste, and get the most out of your cake - and it means perfect party bag-sized pieces of cake.

Feeling inspired to make your own rainbow layer cake or how about some rainbow cupcakes to serve alongside your shopbought cake? And don’t forget to have a look at our easy cake decorating ideas for those of you who want to transform and personalise any of the cakes above.

You might also like our list of Frozen birthday cake ideas or your children might prefer these Bluey birthday cake ideas.

We've also got plenty of first birthday party ideas for those of you thinking of celebrating your little ones' big day, not to mention kids' party games everyone will love, as well as 13th birthday party ideas for your pre-teen.

Jessica Dady
Food Editor

Jessica Dady is Food Editor at GoodtoKnow and has over 11 years of experience as a digital editor, specialising in all things food, recipes, and SEO. From the must-buy seasonal food hampers and advent calendars for Christmas to the family-friendly air fryers that’ll make dinner time a breeze, Jessica loves trying and testing various food products to find the best of the best for the busy parents among us. Over the years of working with GoodtoKnow, Jessica has had the privilege of working alongside Future’s Test Kitchen to create exclusive videos - as well as writing, testing, and shooting her own recipes. When she’s not embracing the great outdoors with her family at the weekends, Jessica enjoys baking up a storm in the kitchen with her favourite bakes being chocolate chip cookies, cupcakes, and a tray of gooey chocolate brownies