Separate the whites and yolks of four eggs, beat the whites stiff, and beat into them one-half cup of granulated sugar. Beat the yolks to a very stiff froth and beat into them one-half cup of granulated sugar. This last mixture must be beaten for exactly five minutes. Add the juice and grated rind of one small lemon; beat yolks and whites together well, then stir in very gently one scant cup of flour that has been sifted three times. Remember that every stroke of the spoon after the flour is added toughens the cake just that much, so fold the flour in just enough to mix well. If baked in small patty pans they taste just like lady fingers. Bake twenty or twenty-five minutes in moderate oven.