1: Toast sourdough bread with butter.
2: In a bowl, combine tuna, mayo, lemon, salt, pepper, red pepper flakes, diced pickles, diced celery, diced red onion, and diced parsley.
3: Spread the tuna salad on the toasted bread.
4: Add avocado and optional tomato slices on top.
5: Place cheddar cheese slices on the sandwich.
6: Enjoy your tuna melt!
