For the sauce, peel and finely dice the onions and garlic. Heat the oil in a pan. Fry the minced meat for about 10 minutes until crumbly. After approx. 5 minutes add half onions and half garlic and fry them.
Season with salt, pepper and oregano. Add the tomatoes and juice, bring to the boil and chop the tomatoes a little with a spatula. Simmer everything for about 10 minutes.
Cook the noodles in 2 l boiling salted water (1 teaspoon salt per litre) according to the instructions on the packet only just firm to the bite, so that they do not break apart during filling.
Clean, wash and drain the spinach. Heat butter in a pot. Fry the rest of the onions and garlic. Add the spinach and let it collapse for 3-4 minutes while turning. Stir in ricotta.
Season to taste with salt and pepper.
Drain the pasta, rinse with cold water and drain well. Dice mozzarella finely. Preheat oven (electric cooker: 225°C/circulating air: 200°C/gas: level 4). Season minced sauce with salt and pepper. Put into 4 small or 1 large casserole dish.
Fill the pasta with the spinach and spread on the sauce. Sprinkle with mozzarella. Bake in a hot oven for about 15 minutes.