In a medium bowl, combine tuna, mayonnaise, celery, onion, garlic powder, and black pepper and mix until evenly combined.
Spread the tuna mixture evenly on two slices of bread.
Sprinkle the cheddar cheese on top of the tuna.
Top with the remaining two slices of bread.
Heat a large skillet over medium-high heat. Place the sandwiches in the skillet and cook for 3-4 minutes on each side, or until golden brown and the cheese is melted.
Remove from the skillet and serve immediately.
Interesting Facts
Tuna is a high-protein, low-calorie food, making it a great choice for a healthy lunch or dinner.
The classic New Jersey Diner style tuna melt is traditionally served on white toast but you can switch it up and use a different type of bread.
Adding diced onion and celery to the tuna mixture adds texture and flavor to the sandwich.