Wash the cabbage and cut it into bite-sized pieces.
Thinly slice the onion and carrot.
Add cooking oil to a pan, then stir-fry the onion, carrot, and cabbage.
Once the vegetables have softened, add the tuna and mix well.
Season with soy sauce, salt, and pepper to taste.
Spoon the sautéed cabbage and tuna over rice.