Julienne the cabbage.
Thinly slice the onion.
Julienne the carrot.
Heat olive oil in a pan and stir-fry onion, carrot, and cabbage.
Once the vegetables are softened, season with salt and pepper.
Drain the oil from the tuna can and add tuna to the pan, stir-frying together.
Top rice with the sautéed vegetables and tuna, then serve in a bowl.