Cut the soft tofu into bite-sized pieces.
Finely chop onion and bell pepper.
Heat olive oil in a pan and sauté the onion and bell pepper.
Add tomato sauce and mix well.
Place the soft tofu in a gratin dish, then top with the sautéed vegetables and sauce.
Generously sprinkle mozzarella cheese on top.
Bake in a 200°C oven for 10 minutes until done.