Shred the cabbage.
Slice the onion thinly.
Pour olive oil into a pan and sauté the onion.
When the onion becomes translucent, add the cabbage and stir-fry.
Drain the oil from the tuna can and add the tuna to the pan. Stir-fry together.
Season with soy sauce and pepper.
Place the stir-fried ingredients on top of rice and sprinkle with sesame seeds.