Cut the tofu into bite-sized pieces.
Finely chop the onion and bell pepper.
Add oil to a pan and sauté the onion and bell pepper.
Add tomato sauce and simmer everything together.
Place the tofu and sautéed sauce in an oven-safe dish.
Generously top with mozzarella cheese.
Bake in the oven at 180°C (356°F) for 15 minutes.