Rainbow cake

Rainbow cake!

It’s fun, colourful and so pretty! My brother has been asking me to bake him a rainbow cake for days. So I thought why not! I don’t think I know anybody that doesn’t like rainbow cake. I mean look at it, it’s so colourful!!!!

It’s basically a coloured vanilla cake with vanilla flavoured swiss meringue buttercream. I personally prefer swiss meringue buttercream over regular buttercream because it’s much lighter and fluffier in texture and it also tastes better. To make the buttercream, you could use either egg whites or you could use meringue powder mixed with warm water. If you don’t have a thermometer, I recommend using meringue powder because you don’t want some sort of food poisoning because of the egg whites. If using meringue powder, mix the powder with warm water, add the sugar and vanilla. Then mix all of this in a double broiler until you can’t feel the sugar granules anymore. Finally, whip it till stiff peaks form and then add the butter.


For cake:

  • 3 ½ cup all purpose flour
  • 2 tsp baking powder
  • 1 ½ tsp baking soda
  • 1 tsp salt
  • 1 cup oil
  • 1 ¾ cup sugar
  • 3 eggs
  • 2 tsp vanilla
  • 1 ½ cup buttermilk
  • 3 drops of red gel food colour
  • 3 drops of orange gel food colour
  • 3 drops of yellow gel food colour
  • 3 drops of green gel food colour
  • 3 drops of blue gel food colour
  • 3 drops of purple gel food colour

For swiss meringue buttercream:

  • 4 large egg whites
  • 300g cold butter cut into pieces
  • 3/4 cup sugar
  • 1 tsp vanilla


  1. Preheat oven to 350F or 180C
  2. Sieve together the flour, baking powder, baking soda and salt. Set aside
  3. In another bowl, whisk the sugar and oil
  4. Next add the eggs and vanilla. Whisk until well combined
  5. Take 6 mixing bowls and put the colours in separate bowls. (so, 3 drops of red in one bowl, 3 drops of orange in another, yellow in the third and so on..)
  6. Add ¼ cup of buttermilk in every bowl and mix with the colour (if you want a darker colour, add more now)
  7. Next, pour ½ cup of batter in every bowl and fold until the buttermilk and colour has incorporated into the batter.
  8. Divide and pour the batter into six 7 inch round baking pans*. Bake for 15-18 minutes (or until toothpick comes out clean when inserted in the middle)
  9. While that’s baking you can make the buttercream by putting the egg whites and sugar in a bowl and whisk it over a water bath (or use a double broiler) until the sugar has dissolved and the mixture reaches 160F
  10. Remove the mixture from heat and transfer it to another bowl.
  11. Using a hand mixer, whisk the egg whites until stiff peaks form (this takes about 10-15 minutes sometimes)
  12. Add the vanilla and butter pieces one at a time (40g at once) and whisk at low-medium speed
  13. Once you start adding the butter, you will notice that the frosting begins to curdle and lose it’s shape, but that is completely normal. It does come back together once all the butter is added and mixed at low-medium for a while
  14. Once the cake has cooled, level all the layers so they are all the same in thickness
  15. Begin with the purple cake, pipe a thin layer of icing and top it with the blue layer of cake. Pipe icing on the blue layer and top it with green. Pipe icing on the green layer and top it with yellow. Finally, pipe the icing on the orange layer and top it with the red layer of cake.
  16. Using an angled spatula, cover the entire cake with a thin layer frosting (crumb coat) and refrigerate for 15-20 minutes
  17. After 20 minutes, cover the cake in another layer of icing and refrigerate for another 20 minutes.
  18. You can use the Wilton 1M tip to pipe flowers on top of the cake.

2 Responses to “Rainbow cake”

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