Drain tuna and place in a bowl. Add cleaned and chopped celery. Mix together ingredients for the dressing: spicey brown mustard, non-fat Greek yogurt, and extra-virgin olive oil. Mix into tuna and celery. Stir in roasted red pepper and fresh ground black pepper to taste.

Clean tomatoes and prepare for stuffing by removing core from the top and gently scooping out the seeds inside, making room for the tuna salad. Carefully stuff the tomatoes with about 1/3 cup of the tuna salad, reserving a little to place between the butter lettuce and tomatoes.

Serve the tuna-stuffed tomatoes atop butter lettuce, placing a thin layer of tuna salad between the tomatoes and lettuce. Sprinkle with crumbled blue cheese and serve with a whole grain roll. Enjoy!