Clean, wash and cut the rhubarb into pieces of about 2 cm. Bring juice, 250 g sugar and rhubarb to the boil. Simmer for about 2 minutes while stirring. Stir 2 tbsp. water and starch until smooth.
Bind rhubarb with it. Put the pot in a cool place. Wash mint, shake dry, pluck leaves from the stalks and chop finely. Mix sour cream, quark, mint and 2 tablespoons of sugar.
Unroll the dough and place it on the baking paper on a baking tray. Spread the sour cream on the dough. Spread 6 tablespoons of compote on top. Bake in the preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: level 4) for about 10 minutes.
Chop the pistachios. Remove the tarte flambée, sprinkle with pistachios and dust with icing sugar. Spread another 6 tablespoons of compote on the dough and cut into pieces. Add the rest of the compote