Clean, wash and cut the rhubarb into pieces. Sprinkle with 50 g sugar and let it stand for a while
Mix quark, 100 g sugar, 9 tablespoons milk, oil, lemon peel and salt. Mix flour and baking powder. Stir half into the quark, knead in the rest. Roll out 2/3 of the dough and press it into the greased fat pan (approx. 35 x 40 cm)
Score the vanilla pod with a knife and scrape out the pulp. Mix with sour cream, whole eggs and 50 g sugar. Spread the rhubarb on the dough. Pour the sour cream and eggs over the dough
Roll out the rest of the dough into a rectangle (approx. 25 x 36 cm). Use a grid roller to roll over twice the length. Carefully pull the dough apart as a lattice, place it on the rhubarb and press on the edge. Cut off any excess dough.
Mix the egg yolk and 1 tablespoon of milk and brush the grid with it. Bake the cake in the preheated oven (electric cooker: 200 °C / convection oven: 175 °C / gas: level 3) for approx. 40 minutes