Separate eggs, beat egg whites until stiff.
Beat butter with sugar and vanilla sugar until fluffy, gradually beat in the yolks, add lemon zest.
Mix flour with baking powder and add to yolk mixture alternately with beaten egg whites, add kirsch.
Grease and flour a baking pan, pour in batter and cover tightly with cherries.
Bake at 180 °C for about 25 minutes.
Divide into pieces, sprinkle with sugar.