Cut the cold butter in small pieces. Then add all other ingredients for the shortcrusts and knead them with your hands to a smooth dough. If necessary, you can add some cold water for the right texture.
Place the dough in plastic wrap in the fridge and let it cool for at least an hour.
During this time wash the plums and core them. I usually use as many plums as fit on the cake. So depending on how you like it best use more or less than 500 g of plums.
Now add all the ingredients for the crumble topping together until you get the wanted texture.
Preheat the oven to 180 degrees Celsius (Ober-/Unterhitze).
Coat a baking tray with butter and flour.
After the shortcrust dough has cooled down, roll it out and use a fork to prick into the dough.
Now arrange the plums as you want and place the crumbles on top.
Bake the cake for 50-60 minutes.
Now you just need to wait until it is cooled down and then enjoy!