Mix the flour, baking powder, sugar and salt in a bowl. Add 2 eggs and the butter, work into crumble.
Place about 2/3 of the crumble on a greased tray and press until it is smooth. Mix the sour cream, vanilla sugar and 2 eggs. Pour the sour cream on the bottom and spread it on.
Place the plum jam on top in thick blobs and spread the remaining crumble on top.
Bake the cake in a hot oven at 200 ° C top / bottom heat for about 30 minutes. After cooling, cut into pieces and dust with powdered sugar.