Beat the egg whites firmly. Mix the soft butter with sugar and egg yolk until creamy, stir in the remaining ingredients, finally fold in the egg whites.
Spread the dough approx. 30 x 20 cm in a prepared tin and bake in a preheated oven at 160 ° for approx. 30 minutes (stick test).
Sprinkle the cold cake with powdered sugar or cover with chocolate icing.