Marmalade Diamonds

Cream together one-half cupful of butter and one cupful of granulated sugar; then add the beaten yolks of three eggs, one-half cupful of sweet milk; then work in two cupfuls of flour into which has been sifted two teaspoonfuls of baking-powder, add the stiffly beaten whites of three eggs and one teaspoonful of lemon extract. Pour into square pan and bake. When cool cut into diamonds. On half of the cakes spread lemon, orange or any good marmalade, and place the other halves on these in sandwich fashion. Cover with yellow fondant flavored with lemon or orange.