About this recipe:A six-layer rainbow cake covered in fluffy white buttercream is sure to garner loads of oohs and ahhs the moment you cut that first slice! Paste food colourings work best, but you can use liquid or gel colouring, too. Best part? The cakes take just 15 to 20 minutes to bake and cool quickly, since they're so thin.
six rainbow food colourings (red, yellow, orange, blue, green, purple)
75g unsalted butter
500g icing sugar, sifted
4 tablespoons milk
1 teaspoon vanilla extract
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Method Prep:1hr › Cook:20min › Ready in:1hr20min
Preheat the oven to 180 C / Gas 4. Grease six 20cm (8 in) round cake tins and line the bottoms with baking parchment. (Read the footnote below if you only have three tins.)
Sift the flour, baking powder and salt together three times. Set aside.
In a separate bowl, beat egg whites until foamy. Add 100g of the sugar gradually, and continue beating only till soft peaks form.
Beat butter until smooth. Gradually add remaining sugar, and cream together until fluffy. Add sifted ingredients alternately with milk a small amount at a time, beating after each addition until smooth. Mix in vanilla. Add egg whites, and fold in gently till no streaks of egg white remain. Divide the cake mixture evenly between six bowls.
Add a few drops of food colouring to each bowl, creating six different coloured cake mixtures. Start with a little food colouring, mix and then add a few more drops if a more vibrant colour is needed. Fill the six prepared cake tins with the cake mixture, each with a different colour.
Bake in the preheated oven for 15 to 20 minutes, or till a skewer inserted into the centre comes out clean. Cool slightly in tin, then remove to cool completely on wire racks.
To make the icing, beat butter until fluffy. Gradually add half of the icing sugar, beating well. Slowly beat in the half of the milk and the vanilla. Slowly beat in remaining sugar. Beat in additional milk, if needed, to make of spreading consistency.
Once the cakes are completely cool, place the first layer on a serving plate or cake stand. Cover the top with icing. Add a second layer and repeat. Repeat till all layers are used. Finally, spread icing all over the top and sides of the cake, smoothing with a palette knife or spatula.
If you don't have six cake tins, you can get by with only three. Simply bake three coloured layers, remove from the oven, let cool slightly and then remove the cakes to a wire rack. The tins should be cool enough to handle by then, so wipe away any cake crumbs left in the tin and then grease with butter and line the bottoms with fresh rounds of baking parchment. Add the three remaining mixtures and bake as before.
Great recipe. Made a rainbow cake with skittles in the centre for my daughter's birthday. Aside from adding the skittles, the only thing I changed was to add philadelphia to the buttercream to make it a delicious cream cheese frosting. Cake is fab, looks amazing, my daughter says it's the best cake in the UNIVERSE! - 16 Oct 2016