Peel onion, chop coarsely. Fry in hot oil. Add tomatoes and stock, braise for 5 minutes. Season with salt and pepper. In the meantime, pluck off the basil leaves and stir in. Roll out the dumpling dough on a floured work surface about 1 cm thick.
Cut out cookies about 4 cm in size. Fill the cookies and sauce alternately into a wide casserole dish. Sprinkle with Parmesan cheese. Cook in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 30-35 minutes.