Rainbow Explosion Cake! - Jane's Patisserie (2024)

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A four layer funfetti sponge cake, with rainbow themed buttercream frosting, a chocolate drip and even more for the best rainbow explosion cake ever!

Rainbow Explosion Cake! - Jane's Patisserie (1)

Rainbow explosion cake

So I was super lucky to reach three quarters of a million followers on Instagram the other day, so I thought I would make an insanely colourful and fun cake to celebrate the occasion! It may seem a bit OTT, but I am a baking blogger after all!

Obviously I only recently made my regular rainbow cake which featured all the colourful sponges, a white buttercream frosting and then lots of colourful sprinkles – so I thought I would switch that cake on its head and create this!

Rainbow Explosion Cake! - Jane's Patisserie (2)


This rainbow explosion cake is based a lot on my funfetti cake sponge – because its a super easy cake to bake, but also so colourful! I did go a little too overboard on the sprinkles, and only had light brown sugar to hand, so my sponge did look a little dark!

The recipe uses caster sugar and I would recommend that over light brown soft sugar for sure – I also used these funfetti sprinkles in the cake because ones that work for funfetti in the UK are so hard to find, and I love these so much!

Rainbow Explosion Cake! - Jane's Patisserie (3)

Rainbow Explosion Cake! - Jane's Patisserie (4)

All the colours!

If you don’t already know, funfetti is like confetti in something, so a cake in this case, and its just fun! But because of the dots of colour in the sponge, I thought I would create a lot of washing up for myself and do a rainbow buttercream outside!

Yes… again… the rainbow only has six colours because it works out much easier, and they are so much more straightforward to do! Red, orange, yellow, green, blue and purple. You can obviously swap these colours up though if you use the recipe for anything!


I used the same colours for the buttercream in this rainbow explosion cake that I did in my other rainbow cake recipe because they work so well, and I am all about reducing the ingredients or added bits like colours that we have to buy!

The method of decorating the cake is fairly faffy if you want the perfect lines like me, but you can also just slap the buttercream on and hope for the best! The best start though is to use some of the base buttercream recipe to do a crumb coat to seal in any crumbs on the cake.

Rainbow Explosion Cake! - Jane's Patisserie (5)

Rainbow Explosion Cake! - Jane's Patisserie (6)


I used the same technique as I did in my mini egg drip cake (there is a YouTube video for this!) and piped rings of colours around the cake after its crumb coat, and then, used my classic large metal scraper to scrape around the edges of the cake to create the smooth and perfect finish!

For the rainbow explosion cakes drip I used a white chocolate drip, but added in some extra white food colouringto make it even brighter – as I just love the bright contrast! This is optional though – or you can add in some colour and make the cake even more colourful, its completely up to you!

Rainbow Explosion Cake! - Jane's Patisserie (7)

Rainbow Explosion Cake! - Jane's Patisserie (8)

With the leftover buttercream from the sides of the cake, I piped them onto a large piece of cling film into a long lines, and then rolled the clingfilm up tightly into a sausage and put this into a large piping bag with my favourite piping tip – I find this the easiest method of multicolour buttercream, but again its optional.

Finishing touches

With swirls of the buttercream, some colourful sprinkles, and some random rainbow style lollipops and some gold candles I had my bright and wonderful rainbow explosion cake! This was randomly thrown together and sort of on the spot so hopefully this post made sense! I hope you love the recipe if you do try it though! x

Rainbow Explosion Cake! - Jane's Patisserie (9)

Rainbow Explosion Cake! - Jane's Patisserie (10)

Rainbow Explosion Cake! - Jane's Patisserie (11)

Rainbow Explosion Cake!

A four layer funfetti sponge cake, with rainbow themed buttercream frosting, a chocolate drip and even more for the best rainbow explosion cake ever!


Category: Cake

Type: Cake

Keyword: Rainbow

Prep Time: 1 hour hour

Cook Time: 30 minutes minutes

Decorating Time: 3 hours hours 30 minutes minutes

Total Time: 5 hours hours

Servings: 20 Slices

Author: Jane's Patisserie



  • 500 g eggs (weigh eggs in shells)
  • 500 g unsalted butter
  • 500 g caster sugar
  • 500 g self raising flour
  • 75 g funfetti sprinkles


  • 750 g unsalted butter (room temp, not stork)
  • 1500 g icing sugar
  • 1 tsp vanilla extract
  • 1-2 tsp red, orange, yellow, green, blue, purple and white food colouring


  • 200 g raspberry jam
  • 180 g white chocolate
  • 75 ml double cream
  • 1/2 tsp white food colouring
  • Rainbow sprinkles


For the Cake

  • Preheat your oven to 170ºC/150ºC fan and line two 8"/20cm springform tins with parchment paper and leave to the side for now.

  • Add the butter and caster sugar to a bowl and beat until light and fluffy.

  • Add in the eggs, and self raising flour and beat again until smooth.

  • Finally add in the funfetti sprinkles and fold through.

  • Bake the cakes in the oven for 60-65 minutes (or until baked - test with a skewer).

  • Once baked, leave the cakes to cool in the tin for 10 minutes before removing to a wire rack to cool fully.


  • Once all of your cakes are cooled, you can make the buttercream.

  • Beat the room temperature unsalted butter on its own for a few minutes to soften it and make it supple.

  • Gradually add the icing sugar beating very well each time until its all mixed in.

  • Keep beating and add the white food colouring and vanilla extract and beat for a few minutes.

  • Get six small bowls, and add 300g of buttercream to each bowl.

  • Colour each bowl into one of your colours with thered,yellow,orange,green,blueandpurple! Leave the leftover buttercream to the side.


  • Split each cake into two sponges, so you have four layers.

  • Using a 10" cake board, add your first layer.

  • Add a couple tablespoons of the buttercream on to the sponge and smooth over. Add a couple of spoons of jam to the middle.

  • Repeat with the second and third layers, and then add the last layer on top.

  • Using the leftover white buttercream, smooth over the sides of the cakes and fill in any gaps and create a crumb coat.

  • Refrigerate or freeze the cake on the board for an hour or so to chill and firm to make the next stage of decorating easier.

  • Once chilled, using a spatula or small piping bags, pipe the colours of buttercream around the sides of the cake.

  • Smooth over using alarge metal scraperuntil the sides of the cake are smooth like in the photos!You may need to add in more buttercream as you go to get the finish you want but this is totally normal!

  • Once this has been done, refrigerate again whilst you make the drip!


  • Add the white chocolate and double cream to a bowl and heat in a microwave in short 10 second bursts stiring well each time.

  • Once melted and combined, add the white food colouring and mix until smooth!

  • Add the ganache to a piping bag and carefully cut off the end and drip down the sides of the cake. The more you push over the side of the cake with the piping bag, the further it will drip!

  • Add the leftover buttercream to a piping bag by adding lines of each colour onto a large piece of clingfilm and rolling this into a sausage.

  • Snip the end off of this, and add to a large piping bag withyour favourite piping tipand pipe swirls of buttercream onto the top of the cake.

  • Finally sprinkle on some sprinkles and leave the cake to set in the fridge fully.

  • In the hot weather I store the cake in the fridge until it has been portioned.



Find my other Recipes on myRecipes Page!

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Rainbow Explosion Cake! - Jane's Patisserie (2024)
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