Cut the tofu into appropriate-sized pieces.
Finely chop the onion and bell pepper.
Heat olive oil in a pan and sauté the onion and bell pepper.
Add the tofu and stir-fry briefly.
Season with salt and pepper.
Transfer the sautéed ingredients into an oven-safe dish.
Evenly pour tomato sauce over the ingredients.
Top with mozzarella cheese.
Bake in the oven at 180°C for 15 minutes.