Finely chop the cabbage.
Drain the oil from the tuna using a strainer.
Chop the onion and green onion.
Add cooking oil to a pan and stir-fry the onion and green onion.
Add the cabbage and stir-fry.
Add the tuna and mix thoroughly.
Add gochujang (Korean chili paste), soy sauce, sugar, and sesame oil to season.
Add the rice and stir-fry until all ingredients and seasoning are well mixed.
Transfer the finished cabbage tuna seasoned rice to a bowl.