Mix the dough ingredients into a batter and spread on a baking sheet lined with baking paper.
Wash the rhubarb and cut into pieces. (The recipe says 600 g. I always do it by eye so that it is enough for a tray. If it doesn`t look too much, I get another pole from the garden). Press the raw rhubarb pieces into the batter.
Bake the base for 30 minutes at 175 °.
Cook a pudding from 700 ml of milk, 80 g of sugar and 2 packets of vanilla pudding powder. Stir 2 cups of sour cream into the warm pudding.
Spread the pudding mixture on the base and bake for another 15 minutes at 175 °.