Mix the butter, sugar and vanilla sugar together until frothy. Grate the skin of the lemon, add the egg yolk, salt and cream, mix everything well. Mix flour with baking powder and add. Mix in the raisins and add a little milk to make the dough more liquid if it gets too thick. At the end add the beaten egg whites and fold in carefully.
Place in a greased Gugelhopf tin and bake at 180 ° for about 50 minutes.