Clean, wash and slice the tomatoes. Peel onions, cut into rings. Pluck off sage leaves, wash and chop. Press the bread dough flat in portions on a floured tray.
Sprinkle the pastry with olive oil. Spread tomato slices and onion rings on top. Season with salt, pepper, sage and dried herbs. Bake the onion patties in a preheated oven (electric: 200 °C/ gas: level 3) for 15-20 minutes.
Slice the parmesan into thin shavings and sprinkle over the onion patties just before serving.