Cut a thin slice from the top of each tomato. Scoop out the pulp and set it aside. Drain the tomatoes upside down on a rack placed over a paper towel. In a skillet, cook bacon until well done (or microwave until done). If done in skillet, drain off fat and then add the pepper and onion and sauté until soft. Remove the pan from heat and blend in the cheese, lettuce and reserved tomato pulp. Fill each tomato shell with half the mixture. Sprinkle with cracker crumbs and dot each with 1 tsp. of butter. Place in a baking dish sprayed with non-fat cooking spray (or buttered dish). Bake in preheated 400* oven for 25 to 30 minutes.