Knead everything for the meatballs well together and form balls (the size of a ping pong ball). Brown the balls in oil in a roasting pan that can also go in the oven. Remove the balls from the pan and set aside.
Preheat the oven to 200 °C.
Cut the bell peppers in half. Remove the stem and seeds and cut into fine strips.
Place the bell peppers in the roasting pan, drizzle with some oil, season with pepper and salt, and roast for 25 minutes in the preheated oven at 200 °C.
Combine the passata, half of the roasted bell peppers, garlic, and onion with the ricotta in a tall measuring cup. Blend everything finely with an immersion blender.
Mix the sauce with the al dente cooked penne in a large bowl, along with the meatballs and the other half of the roasted bell peppers. Mix everything well and top with the slices of mozzarella.
Gratin for about 30 minutes in an oven at 200 °C until you have a nicely colored crust.
Tips
Sometimes I also prepare it completely veggie and replace the minced meat with fried eggplant cubes.