Cut the tofu into bite-sized pieces.
Finely chop the onion and bell pepper.
Heat olive oil in a pan and sauté the onion and bell pepper.
Add tomato sauce and bring to a simmer.
Place the cut tofu into a gratin dish.
Top the tofu with the sautéed vegetables and sauce.
Sprinkle shredded cheese on top.
Bake in the oven at 200°C for 10 minutes.