The butter mix of foam with sugar, gradually add whole eggs and premixed with baking powder, flour and starch. Finally, add a little grated lemon or orange peel, rum and chocolate, broken into small pieces. Pour dough into greased with butter form and bake at 180 ° C about 50 minutes. Hot cake sprinkle with powdered sugar or icing smeared with the following: in a broader porcelain bowl whisk wooden spoon powdered sugar, lemon juice and 3 tbsp boiling water, until mixture thickens and turns white. The glaze is applied while still hot. Smoothed with a knife. Optional can be colored with a harmless dye.