Cut the tofu into bite-sized pieces.
Chop the onion, bell pepper, and broccoli into small pieces.
Heat olive oil in a pan and sauté the onion, bell pepper, and broccoli.
Season with salt and pepper.
Place the sautéed vegetables and tofu into a gratin dish.
Pour the tomato sauce over and mix well.
Top with mozzarella cheese.
Bake in the oven at 200°C (392°F) for 10–15 minutes.