Shred the cabbage.
Thinly slice the onion.
Heat olive oil in a pan and sauté the onion and cabbage.
Season with salt and pepper.
Drain the oil from the canned tuna and set aside.
Place the sautéed vegetables on top of the rice.
Add the tuna on top of the vegetables.
Finish with soy sauce or chopped green onions as a garnish.