01 -
In a bowl, combine the drained tuna, mayonnaise, diced celery, diced red onion, chopped pickles, salt, and pepper. Mix thoroughly until evenly incorporated.
02 -
Layer the tuna mixture between slices of bread with cheddar cheese to form sandwiches.
03 -
Spread butter evenly on the outer sides of each sandwich. Grill in a preheated pan over medium heat until the bread is golden and cheese is melted, approximately 4 minutes per side.
04 -
Slice the grilled sandwiches diagonally and serve immediately while warm.