Preheat oven (electric cooker: 225 °C/recirculating air: 200 °C/gas: level 4). Roll out the dough on the baking paper. Place in a square tart tin (21 x 28 cm) or on a tray. Fold down the edges and press down
Spread half the sour cream on the dough base. Clean and wash the bell peppers and spring onions and cut them into strips or pieces.
Spread everything out on the cake. Season with salt, pepper and oregano. Spread the rest of the sour cream as a blob
Sprinkle with grated cheese. Bake the tart in a hot oven on the lowest shelf (gas: see oven manufacturer) for approx. 20 minutes