The gorgeous rainbow cake has been made with the base recipe of Butter Cake. Butter cake is great as it has the right depth of texture to hold it's height and the icing.
4 large eggs (separated)
2 3/4 cups of sifted flour
4 teaspons baking powder
1/2 teaspoon salt
1 cup of unsalted butter at room temperature
2 cups of white sugar (1 1/2 cups to beat with butter and 1/2 cup to beat with egg whites
2 teaspoons vanilla
1 cup milk
1/4 teaspon cream of tartar
Food colouring (red, orange, yellow, green, blue, purple - note if you don't have all the colours you can of course mix to make the right colours)
Preheat the oven to 180 degrees c. Butter and flour a 20cm round bake tin. You may like to line the bottom with baking paper.
Separate the eggs, placing the yolks in one bowl and the whites in another. Allow the eggs to come to room temperature.
Sift flour, baking powder and salt together.
Beat the butter and 1 1/2 cups of sugar together until light and fluffy. Add egg yolks. one at a time, beating after adding each. Add the vanilla extract. Add the flour and milk to mixture.
In a separate bowl whisk the egg whites until foamy. Add the cream of tartar and keep beating until soft peaks form. Slowly add the remaining 1/2 cup of sugar and continue to beat until stiff peaks form. Gently add the whites into the batter and mix being careful not to over mix or the batter will deflate.
Divide the batter evenly into 6 separate bowls (you'll get just over a cup in each bowl. Add colour to each bowl until it is the right depth of colour - around about 6 drops is enough give or take.
Add one bowl of mix to the 20cm round baking tin and bake for 15 minutes (or until cooked depending on your oven). Remove from oven and allow to cool on baking tray. Note: giving the tin a little shake helps to move it away from the edges of the tin if you have buttered and floured the tin well. Repeat adding each mixture and cooking for 15 minutes each until cooked. If you have 6 x 20cm baking tins then you could do them all at once
If you have time put the cakes in the fridge overnight so they are easier to ice, and also so that the slice open nicely. To ice the cake - the cake should be layered with red at the top and purple at the bottom as per layering below:
8 cups icing sugar
2 cups of unsalted butter
2 teaspoons vanilla
8 tablespoons milk
Beat the butter until smooth, add the vanilla extract then with the mixer on low speed gradually add icing sugar scraping the sides as needed. Add milk and beat frosting on high speed until light and fluffy (about 5 minutes)
The icing can be stored for up to 10 days.
To ice the cake place the bottom purple layer down then add icing between layers, adding the blue layer next. The edges may need a little more icing to even the cake out as the sides sink a little. Once all layers are placed and iced, using a large bakers spatula, place the icing around the outside of the cake and on top smoothing it over until neat and 'tidy'. You can decorate the outside as you wish. We have used 6 ribbons reflecting each colours layer of cake underneath the icing. Simply measure the ribbon around and cut to fit. Wrap the ribbon around the cake and pull a little tightly in so that it lightly embeds in the icing and you're done! Congratulations! It's a bit of a long recipe but so much fun seeing everyone's face's once you have made it and you deserve the credit you'll get :) He he!
OH and happy birthday to whomever you're making it for enjoy!