Cut tofu into bite-sized pieces.
Finely chop onion and bell pepper.
Add olive oil to a pan and sauté onion and bell pepper.
Add tofu and stir-fry together.
Season with salt and pepper.
Place the cooked ingredients in an ovenproof dish and top with tomato sauce.
Add mozzarella cheese on top.
Bake in the oven at 180°C (356°F) for 10 minutes.