Preheat oven to 160 degrees (Celsius). Grease the baking tin and cover it with some flour. Let the butter sit at room temperature. Mix the flour with the baking powder. Separate the egg whites in a bowl and beat them with a pinch of salt until stiff. Mix the egg yolk with sugar, butter and vanilla sugar. Add STROH rum, milk and the flour/baking-powder. Stir it with coconut flakes, lemon juice and dried cranberries and add it to the egg whites. Pour the dough into the cake tin and bake it in the preheated oven for 50 minutes. Serve with confectioner’s sugar.