A cut pastel rainbow cake showing its rainbow layers, with slices on pink plates and forks, from above

Cakes & Cupcakes

Pastel Rainbow Cake

There is something really spectacular about cutting into a frosted cake to reveal several different colourful layers of happiness and fun.

A whole pastel rainbow cake with ridged pale yellow frosting and a ring of meringue kisses, pink tulips behind A tall slice of pastel rainbow cake on a pink plate, the cut cake behind

Who doesn't love rainbow cakes?! They look as fabulous as they (should) taste! It was my niece's birthday a few weeks ago and since I could not be there in person, I virtually celebrated by baking this fun cake.

Rainbow cakes are usually simple sponge cakes dyed with different colours sandwiched with layers of buttercream in between. Whilst they are amazing to look at, they can quickly become far too sweet after a few bites. To avoid this, I have reduced the sugar in the cake, used cream cheese frosting in between the layers and frosted the outside with Swiss meringue buttercream (which is still sweet, but less sweet than American buttercream).

As there are at least six layers, you want a cake that is firm enough to stand tall, without the bottom layers being too compressed and unstable. This should not come at the expense of sacrificing on a light and fluffy texture, however – meaning that I had to create a recipe which balances both of these requirements.

Close-up of the meringue kisses on the edge of a pastel rainbow cake, pink tulips behind

Also, admittedly, baking this cake does require a bit more patience (though only very moderate skill). I therefore prefer to make cream cheese icing at least a few days in advance and keep it in the fridge. The Swiss meringue buttercream needs to be stored at room temperature, so make that no more than two days in advance. The cakes can be made up to four days in advance and frozen. I therefore needed a recipe which was robust enough to still be moist after a few days.

A slice of pastel rainbow cake with meringue kisses in front, the cake stand behind

This is as tall a cake as it is big, so it is great for a special occasion when you have to cater for guests. I have added tips for storage and assembly after the recipe, to make sure you get those pretty perfect layers. I hope you enjoy this recipe as much as I do.

I decorated it with the rainbow meringue kisses which I made in a previous post.

PS. I have tried these as cupcakes and they are ok, but I am not convinced, so you can use the recipe for cupcakes, but I think it needs more tweaks and modifications which I am working on 🙂

A whole pastel rainbow cake ringed with meringue kisses beside tulips and a pink plate, from above A slice being lifted out of a pastel rainbow cake, showing the rainbow layers

The recipe

Pastel Rainbow Cake

adventureswithsugar.com/pastel-rainbow-cake/

Method

Method: rainbow cake

  1. Preheat the oven and prepare the tins: Preheat your oven to 180˚ Celsius. Grease and line the bottom and sides of two 20cm cake tins.
  2. Sift the dry ingredients: Sift the flour, cornflour, baking powder, bicarbonate of soda and salt into a bowl and set aside.
  3. Whisk the butter, oil and sugar: Place the melted butter, oil and sugar in a bowl and whisk to combine, about a minute (I usually just use a hand whisk).
  4. Add the eggs and vanilla: Then add the eggs and vanilla and whisk again, about a minute.
  5. Don't overmix: You want to mix only until incorporated. The more you mix, the more the cake will dome, which you don't want!
  6. Add a third of the flour: Add a third of the flour to the sugar and egg mixture and gently whisk in.
  7. Add the buttermilk: Then add the buttermilk.
  8. Add the rest of the flour and milk: Add another third of the flour and mix, followed by the milk and finally the last batch of flour.
  9. Divide and colour the batter: Divide the batter equally between two bowls and tint the batter with the gel food colours, to your desired colour.
  10. Bake: Place into a preheated oven to bake for 25 minutes or until a skewer inserted comes out clean.
  11. Watch it carefully: You want to watch it carefully! Leaving it in for too long will result in browning, which you do not want.

Method: cream cheese frosting

  1. Cream the butter: Cream the butter until light and airy.
  2. Add the icing sugar: Then add in the icing sugar and beat until combined.
  3. Beat the cream cheese: In a separate bowl, beat the cream cheese until smooth.
  4. Fold in the cream cheese: Then gently fold the cream cheese into the butter and icing sugar mixture.
  5. Why beat it separately: Beating the cream cheese separately ensures that it is not overbeaten, and your icing does not end up being too runny.

Method: white chocolate Swiss meringue buttercream

  1. Melt the white chocolate: Melt the white chocolate with the oil and set it aside.
  2. Prepare the double boiler: Fill the bottom of the saucepan with water and bring to a gentle simmer, not an aggressive boil (or you will have water flying everywhere!).
  3. Combine the egg whites and sugar: Place the egg whites and sugar in a bowl that sits over the saucepan, and place it over the hot water.
  4. Stir gently: You want to gently stir this continuously with a whisk to make sure that the eggs do not scramble and that the sugar dissolves, but not so aggressively that you aerate the eggs too much.
  5. Check the sugar has dissolved: Continue to do this until the sugar has dissolved into the egg. Rub a bit of the mixture in between your two fingers and if it is not grainy, the sugar has dissolved.
  6. Whip the meringue: Transfer this mixture to a stand mixer (or hand mixer, but you will have to be patient!) and continue to whip for around 10 minutes until your meringue is light and fluffy, and cool to the touch.
  7. Add the butter: Then add in the butter, block by block, and whip in, until the buttercream is thick, glossy and velvety.
  8. Add the vanilla: Add in the vanilla extract if using.
  9. Add the white chocolate: Once the white chocolate is cool to the touch, add that in too and whip until incorporated.
  10. Store: Store the buttercream at room temperature.
Tips for storage
  • Make the cream cheese icing 5 days in advance and store in the fridge.

  • Bake the cakes four days in advance. Once they are out of the oven and cooled to room temperature, wrap them in cling wrap fully, and store in the freezer.

  • Do not stack them one atop the other as they are fairly soft cakes, so will compress over time.

  • Make the Swiss meringue buttercream at least two days before assembling the cake and store at room temperature.

Tips for assembly
  • In order for the perfect colours of the sponge to be seen once the cakes are frozen, I take them out at least a day before and level off the top of the cake, to remove any dome.

  • I also gently trim around the sides of the cake to remove any browning which may have occurred. I use a sharp knife and do it freehand, making sure to cut very little off.

  • If you are not confident in doing this, use a circle template with a 19.5cm diameter.

  • Alternatively, if you are not fussed with perfection, like I am, you can leave as is.

  • I do recommend cutting off the tops though so the layers are level.

  • Finally, as this is a tall cake, to make sure it does not lean, insert four skewers into the cake to give it stability and support.

  • Once your cakes have been layered and filled with the cream cheese icing, put in the fridge for an hour to let it firm up. Then frost the sides with the Swiss meringue buttercream.

  • Feel free to DM me on Facebook or Instagram should you have any questions.

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