Wash the plums, dab dry and cut in half. Remove stones and cut the flesh into slices. For the sponge mixture, mix fat, sugar and vanilla sugar until creamy. Stir in eggs bit by bit. Mix flour and baking powder and add to the egg-fat mixture with the cream. Stir well. Put the dough into a springform pan (28 cm Ø) lined with baking paper and smooth it down.
Spread plum wedges close together. For the crumbles, knead fat, flour, sugar, cinnamon and salt to crumbs and sprinkle over the plums. Bake the cake in a preheated oven (electric: 200 °C/ gas: level 3) for 50-60 minutes. Let the cake cool down on a cake rack. Mix icing sugar and lemon juice for the icing. Spread as a blob on the cake. Results in about 16 pieces