How To Make A Rainbow Cake
1. Preheat your oven to 175 degrees. Brush six 9-inch round cake pans with margarine. Line the bottom of each cake pan with parchment; brush again and set aside.
2. Whisk the flour, baking powder and salt in a large bowl and set aside. Cream together butter and sugar. Slowly add egg whites and mix until well combined. Add vanilla and mix until fully incorporated. Add flour mixture and milk in two alternating additions, beginning with the flour and ending with the milk. Mix until well combined.
3. Divide the mix evenly between six medium bowls. Add food colouring to each bowl and whisk until desired shade is reached. Transfer each colour to an individual cake pan. Transfer to oven and bake until a knife inserted into the centre of each cake comes out clean
4. Remove cakes from oven and transfer to a wire rack; let them cool for 10 minutes. Invert cakes onto a wire rack; re-invert and let them cool completely.
5. Using a serrated knife trim tops of cakes to make level. Place four strips of parchment paper around perimeter of a serving plate. Place the purple layer on the cake plate. Spread a thin buttercream filling over the first layer with a small spatula so it extends just beyond edges. Repeat process with blue, green, yellow, and orange layers.
6. Place the remaining red layer on top, bottom-side up. Gently sweep away any loose crumbs with a pastry brush. Using a spatula to cover the top and sides with a thin layer of buttercream. Refrigerate until set – it should take about 30 minutes.
7. Using your spatula, cover the cake again with the remaining buttercream.
(Recipe c/o Martha Stewart <3 http://www.marthastewart.com/256688/rainbow-cake )