Clean and wash the rhubarb, dab dry and cut into 1-2 cm long pieces. Sprinkle with 50 g sugar and let it stand for a while. For the dough mix quark, 100 g sugar, milk, oil, lemon peel and salt.
Mix flour and baking powder. Stir half into the quark mixture, add the remaining flour and knead to a smooth dough. Roll out 2/3 of the dough on a floured work surface and line a greased fat pan (33x 35 cm) sprinkled with breadcrumbs.
Cut the vanilla pod lengthwise and scrape out the pulp. Mix sour cream, eggs, remaining sugar and vanilla pulp. Spread the rhubarb on the dough and pour over the sour cream. Roll out the remaining dough to a rectangle (approx. 36x25 cm).
Using a grid roller, roll over the dough twice lengthwise and pull the dough apart as a grid. Place the dough grid on the rhubarb and cut off any excess dough. Mix egg yolk and cream and spread the grid with it.
Bake in the preheated oven (electric cooker: 200°C/ gas: level 3) for approx. 40 minutes. Results in about 24 pieces.