Cut the tofu into bite-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 to the pan and grill until slightly golden.
Transfer the sautéed ingredients to an oven-safe dish.
Pour tomato sauce over the ingredients.
Generously top with mozzarella cheese.
Bake in the oven until the cheese has melted.