Take one cup of powdered sugar, one-half cup of butter rubbed to a cream; add yolks of six eggs and stir until very light. Then sift two cups of flour with one and one-half teaspoons of baking-powder sifted in well (sift the flour two or three times). Grate in the peel of a lemon or an orange, add the juice also, and add three-quarters cup of milk alternately with the flour. Bake in moderate oven.