Slice the cabbage into thin strips.
Finely chop the onion.
Heat olive oil in a pan and sauté the onion.
When the onion becomes translucent, add the cabbage and stir-fry.
Drain the oil from the tuna and add it to the pan, stir-frying together.
Add rice and season with salt and pepper.
Mix and stir-fry everything together until well combined.