4 oz self-raising flour
4 oz sugar
4 oz butter
2 eggs
1 orange

Cream butter and sugar, add grated zest of the orange. Beat in eggs, orange juice and flour. Bake in a well-greased and floured tin in a moderate oven, until the cake leaves the sides of the tin and a skewer inserted comes out clean. Remove from tin and cool on a wire rack.
If liked you can ice with orange icing - I just make a water icing, substituting orange juice for water.
I always bake this in a kugelhopf mould. You can substitute other citrus fruit if liked; I often make it with lemon.