1. Start by washing, drying and pitting the plums. To remove the stone from the plums, use a sharp knife and cut the plums on one side along the stone. Do not halve them completely, you should have plums that are almost in one piece. Set them aside.

2. For the streusels add the flour, sugar, vanilla extract and butter in small pieces to a bowl and mix (works best with a fork or your fingers) until different-sized streusels form. Add the sliced almonds and cinnamon (optional) and mix in. Place in the fridge until needed.

3. Add the quark, sugar, milk, vegetable oil, vanilla extract and egg to a large bowl and mix until well combined. Mix the flour with baking powder and salt. Add it to the bowl and knead until the dough comes together. The dough will be quite soft.

4. Preheat the oven to 200°C (390°F). Line a (deep-dish) baking sheet with baking parchment or grease it. Roll out the dough on a floured surface to the size of the baking sheet and transfer the dough. Press/pull the dough into shape if you have problems rolling it out due to its softness.

5. Open the plums so they look like little butterflies – you want them still connected on one side. Place them close to each other on top of the dough. They should cover everything. Distribute the streusels evenly on top of the plums and sprinkle some pearled sugar on top as well (optional). Bake the cake for about 25-35 minutes. Take it out of the oven and let it cool down. Serve slightly warm or completely cooled.