Beat butter with sugar, vanilla sugar, a pinch of salt and eggs until frothy. Mix flour with baking powder and ground almonds and stir into the butter and egg mixture. Fold in rum as desired. Pour the dough into a greased springform pan (30 cm).
Wash the nectarines, cut them in half and remove the stones. Cut the halves into 3 wedges. Spread the nectarine wedges on the dough like a roof tile. Put the cake in the oven at 175 degrees.
In the meantime, mix the flaked almonds with the powdered sugar and spread over the cake after baking for 20 minutes. Then bake for another 20 minutes. Cover the cake with baking paper about 10 minutes before the end of the baking time.
Tip: You can also prepare the cake in a tart form and then serve it warm as a dessert with vanilla ice cream, whipped cream or vanilla sauce.