Finely chop the tofu, onion, carrot, and bell pepper.
Heat oil in a pan and sauté the onion, carrot, and bell pepper.
Add tuna (drained of oil) and tofu, and stir-fry well together.
Season with soy sauce, salt, and pepper to taste.
Place the stir-fried tofu, vegetables, and tuna mixture on top of the rice.