For the fruit cake, cream the soft butter with powdered sugar, vanilla sugar and lemon zest, add the rum. Stir in the yolks one by one. Whip the egg whites with the sugar until stiff, mix the flour with the baking powder and fold into the yolk mixture alternately with the whipped cream. Pour the dough into a greased, floured baking pan. Smooth out and spread any fruit on top.
Preheat oven to 170 degrees and bake cake for about 40 minutes. After baking, let cool and sprinkle with powdered sugar. The fruit cake tastes very good with apricots, plums, cherries…….