In a medium bowl, combine the drained tuna, diced celery, red onion, pickles, mayonnaise, salt, and pepper. Stir until evenly mixed. mix

Lay out the sourdough bread. Place a slice of cheddar cheese on each piece. Divide the tuna mixture between four slices of bread. Top with the remaining slices to form the sandwiches. assemble

Heat 1 tablespoon butter in a medium skillet over medium heat. Place two sandwiches in the skillet and cook for 3-4 minutes, until golden brown. Flip the sandwiches and add another tablespoon of butter. Cook for an additional 3 minutes. finish

Repeat the process with the remaining sandwiches, adding butter as needed. finish