Put the tuna, egg, and cheese in a medium-size bowl.
Season with the salt and mix well with a fork to combine the ingredients.
Divide the tuna mixture into 4 equal portions and shape each portion into a patty about ½ inch thick.
Preheat a large skillet over medium-high heat until hot but not yet smoking, about 3 minutes. Drop in the butter and swirl to coat the pan. Place the patties in the pan and pan-fry for 2 to 3 minutes, until browned on the bottom. Flip and cook for 2 to 3 minutes more, until browned on the other side. Serve immediately with a knife and fork, or let cool for a few minutes until easy to handle and eat as a handheld meal.
