Shred the cabbage and lightly salt it.
Drain the oil from the canned tuna using a strainer.
In a bowl, combine cabbage, tuna, mayonnaise, and pepper, and mix well.
Place a sheet of seaweed on the sushi mat and spread the rice thinly.
Add the cabbage tuna filling on top of the rice.
Roll it up tightly to make gimbap.
Cut into bite-sized pieces.