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 lightly stir-fry.
Season with tomato sauce, salt, and pepper.
Place the tofu and sautéed vegetables in an oven-safe dish.
Top with mozzarella cheese.
Bake in a preheated oven at 180°C (356°F) for 10 minutes.