Cut the tofu into bite-sized pieces.
Finely chop the onion and bell pepper.
Add olive oil to a pan and sauté the onion and bell pepper.
Add the tofu and lightly stir-fry.
Pour in the tomato sauce and mix well with the ingredients.
Transfer the sautéed mixture into a gratin dish.
Sprinkle mozzarella cheese on top.
Bake in the oven at 200°C for 10–15 minutes.