Preheat oven to 190C. Line and grease a 25cm round or square cake tin.
Beat eggs for 10 minutes. Slowly add sugar, then beat for another 10 minutes.
Sift flours, soda and cream of tartar 3 times. Gently fold into eggs and sugar with either a metal spoon or spatula.
Pour into tin and place in the upper half of oven.
Bake for 15-20 minutes. Turn sponge a quarter turn each 5 minutes.
Cake is cooked when the top springs back when touched.
Cool on wire rack, wrapped in a clean tea towel.
Fill and ice as desired.
