Plum quark cake with almond crumble sounds complicated, but it is not. Although it has three layers, it is very easy to make: you prepare the layers (stoning the plums takes the most time), stack them in the tin one after another, and the oven does most of the work.
It is a moist cake with a sponge base, a quark filling with plums and a crumble topping finished with almonds. It cuts into plenty of pieces and is firm enough to travel, so we like to make it for celebrations, picnics and grape harvests. It is best the next day, so we bake it the day before.
Finally, make the sponge batter. Whisk the eggs, sugar and vanilla sugar at the highest speed for 3–5 minutes, until the mixture increases in volume and turns pale. Mix in the oil and sour cream, then, mixing constantly at low speed, add the flour mixed with the baking powder. You will have a fairly thick sponge batter.
Crumble the crumble over the plums, taking it out of the fridge only now.