Preheat oven to 325°. In a large bowl, combine tuna, mayo, Dijon, celery, lemon juice, and dill. Mix until combined and season with salt and pepper.
Slice pickles in half lengthwise. Using a spoon, scoop out the seeds to create boats. Place pickles on a small baking sheet, fill with tuna salad and top with sliced tomatoes. Sprinkle all over with cheddar and place in the oven. Bake until cheese is melted, 8 to 10 minutes. Serve.
Recipe by Cooking TV Recipes at https://cookingtv-channel.com/tuna-melt-pickles/