How to cook
Mix the butter with half the sugar until you get a foam. Add the egg yolks one by one, then the raisins and grated lemon rind.
Mix the egg whites with the remaining sugar, pour them out gradually into the yolk mixture and add the flour. Mix well and fill cupcake forms carefully with the mixture up to 2/3 of their volume.
Bake them in a moderate oven until golden.