In a large bowl, combine the drained tuna, breadcrumbs, mayonnaise, cheddar cheese, onion, celery, egg, Dijon mustard, garlic powder, salt, and black pepper. Mix until well combined.
Shape the mixture into patties, about 3 inches in diameter and 1/2 inch thick.
Heat olive oil in a large skillet over medium heat. Once hot, add the patties to the skillet, making sure not to overcrowd the pan.
Cook for about 4-5 minutes on each side, or until golden brown and heated through. Remove from the skillet and place on a paper towel-lined plate to drain excess oil.
Serve warm, optionally with additional cheese melted on top or on a toasted bun.