Set the cheese out so it begins to come to room temperature.
4 - 1 Oz. Slices Sharp Cheddar Cheese
After draining the canned tuna, use a fork to break it into small chunks and transfer to a mixing bowl.
5 Oz. Canned Tuna in Water
Mix in the celery, onion, pickle, lemon juice, a pinch of salt, two pinches of pepper and 2 Tbsp of the mayo. Test for more salt and pepper and then set this mixture (tuna salad) aside.
6 Tbsp Mayonnaise, 1 Tbsp Minced Onion, 1 Tbsp Finely Diced Celery, 1 Tbsp Pickle Relish or Finely Diced Pickle, 1/2 tsp Lemon Juice, Salt and Pepper to Taste
Begin building the melts. Spread 1/8 of the remaining mayo on one side of a slice of bread and place it (mayo side down) in a cool skillet/pan. Place the pan on your stove and turn the heat to medium or medium/low (depending on how powerful your stove is). The ultimate goal is to get everything melty inside the melt without over-toasting the bread.
4 Slices Sandwich Bread
While the pan begins to heat up, build the rest of the sandwich. Add another 1/8 of mayo to the second side of bread while it sits in the pan. Add a slice of cheese on top of that, then half of the tuna salad. Top with another slice of cheese.
Add 1/8 of mayo to a second slice of bread and place it, mayo side down, onto your under-construction sandwich. Press down just a bit to help mash everything into place.
Add another 1/8 of mayo to the second side of this second piece of bread (that will be the lubrication for when you flip the sandwich over.
After the sandwich is assembled, go ahead and flip it. Press down one more time to help mesh everything together - being careful not to squeeze the insides out of the sandwich.
Flip the sandwich every 1-2 minutes until both pieces of bread are nicely toasted, the cheese is melted and the tuna salad is hot. Remember, the goal is not to burn the bread while everything cooks. Flipping the sandwich can help prevent burning to some degree. Serve right away with your favorite sandwich sides (note: if you cut the sandwich, be sure to let it rest 4-5 minutes beforehand. Otherwise, it could get a little runny).