Cut the napa cabbage into bite-sized pieces.
Julienne the onion and carrot.
Drain the oil from the canned tuna using a strainer.
Heat a pan with cooking oil and stir-fry the onion and carrot.
Add the cabbage and stir-fry until it softens.
Add the tuna, then season with soy sauce and pepper.
Once everything is well mixed, serve it over rice.
If desired, sprinkle with sesame seeds to finish.