Mix the ingredients for the dough into a batter and spread on a baking sheet.
For the topping, mix the quark, eggs, pudding powder, lemon zest and lemon juice as well as sugar to a smooth mass and distribute evenly on the dough. Place the halved plums (also works great with frozen fruits) on top like a roof tile.
For the crumble mix the flour, sugar and cinnamon. Work the melted butter slowly into the flour mixture with a fork. Spread the streusel over the plums.
Bake in the preheated oven on the middle rack at 180 degrees for about 40 minutes.