Wash, drain and stone the plums. Cream fat, 200 g sugar and vanillin sugar. Stir in eggs. Add ground hazelnuts, milk and rum. Mix flour and baking powder and stir into the dough.
Spread the hazelnut dough on a greased and floured baking tray (40x35 cm). Cover with plums and sprinkle with 1-2 tablespoons of sugar. Bake in the preheated oven (electric cooker: 200 °C/ gas: level 3) for 20-25 minutes.
In the meantime beat the egg whites until stiff. Stir in the remaining sugar and lemon juice. Finally stir in cinnamon. Pour into a piping bag with star-shaped spout. Spray approx. 20 tuffs on the plum cake and bake again in the preheated oven (electric range: 175 °C/ gas: level 2) for 15 minutes until the meringue begins to brown slightly.
Leave to cool and cut into 20 pieces. Serve sprinkled with hazelnut leaves. Makes about 20 pieces.