- Prep the ingredients per the instructions above.  
- Flake the tuna with a fork, then combine it with the mayonnaise, onion, celery, relish, lemon juice, salt, and pepper. 
- Slather one side of each piece of bread with mayonnaise (like you would using butter), then place into a large skillet, mayonnaise side down. 
- Place a cheese slice onto the bread. Spread the tuna mixture over the cheese slices. Place a cheese slice on top. 
- Use the mayo to "butter " the remaining two slices, then place on top, mayonnaise side up and out. 
- Heat the pan to medium heat and cook until the bread is lightly browned on the bottom. 
- Flip the sandwiches carefully to the other side, then cook until the other side has browned. 
- Slice in half and serve with chips, pickle, and lemonade.