Wash and julienne the cabbage.
Thinly slice the onion.
Drain the oil or water from the canned tuna using a strainer.
Heat olive oil in a pan and sauté the onion first.
When the onion turns translucent, add the cabbage and stir-fry.
Once the cabbage softens a bit, add the tuna and stir-fry together.
Season with salt and pepper.
Serve in a bowl as a rice bowl.