Shred the cabbage.
Slice the onion thinly.
Heat olive oil in a pan and sauté the onion.
When the onion becomes translucent, add the cabbage and sauté.
Drain the oil from the canned tuna and add it to the pan, stir-fry together.
Season with salt and pepper.
Put rice in a bowl and top with the stir-fried ingredients.