For the tortelloni, boil 2-3 litres of salted water (approx. 1 teaspoon salt per litre). Clean the broccoli, cut into florets and wash. Peel onion and garlic and dice finely. Cut mozzarella into slices.
Preheat oven (electric cooker: 225°C/circulating air: 200°C/gas: level 4). Add tortelloni to boiling salted water and cook according to package instructions. Add broccoli about 4 minutes before the end of the cooking time.
For the sauce, heat oil in a saucepan. Sauté the onion and garlic in it. Add the chunky tomatoes, bring to the boil and simmer for about 5 minutes. Grease a casserole dish.
Drain the pasta and broccoli, collecting about 100 ml of pasta water. Stir into the sauce, season with salt, pepper and 1 pinch of sugar. Pour the tortelloni mix into the tin. Pour tomato sauce over it, place mozzarella on top.
Bake in the oven for 8-10 minutes.