Cut the tofu into bite-sized pieces.
Slice the onion and bell pepper.
Heat olive oil in a pan and sauté the onion and bell pepper.
Add the tofu and lightly stir-fry.
Season with salt and pepper.
Place the stir-fried ingredients in an oven-safe dish and pour tomato sauce over them.
Top with mozzarella cheese.
Bake in a preheated oven at 180°C for 10 minutes.