Finely chop the cabbage.
Slice the onion and carrot into thin strips.
Heat cooking oil in a pan and stir-fry the cabbage, onion, and carrot.
When the vegetables soften, add tuna and stir-fry together.
Season with soy sauce, salt, and pepper.
Place the stir-fried mixture on top of the rice.
Add a fried egg on top (optional).