Pre-heated oven 1800C, grease a 8”spring form tin, line with baking paper and lightly dust with flour
Cream butter and sugar till light and fluffy. Add eggs one at a time until combined. Add sifted dry ingredients and mix until all combined.
Split mix in half and add lemon rind and yellow food colouring and mix till all is combined. Repeat with the orange.
Put cake mix into 2 piping bags and pipe one colour on top of the other until all cake mix is used. Turn the tin in circles to distribute the mix evenly in the tin and cook for 45 minutes.