Wash the plums and cut in half. Then core and mix with sugar and cinnamon. Let it steep for about 10 minutes. Preheat the oven to 150 ° C. Spread a thin layer of butter on a baking dish.
Cut the Striezel into 1 cm thick slices. Layer half of the slices in the pan and spread the plums on top. Cover with the remaining Striezel slices.
Warm milk. Stir in eggs, sugar, vanilla sugar, a pinch of salt and grated lemon zest.
Pour egg milk over the pyre and bake in the oven for about 50 minutes. Serve sprinkled with powdered sugar. Serve lukewarm.