Cut the top from each tomato, cutting a scallop edge 1/2 to 1 inch from the top. Use a spoon to scoop out tomato pulp. Set upside down on paper towels to drain. Meanwhile, in a 10-inch skillet cook bacon until crisp; drain, reserving 2 tablespoons drippings. Crumble bacon and set aside. Cook onion in reserved drippings over medium heat until tender; stir in spinach. Reduce heat to medium-low. Cook, covered, until spinach is wilted, 1 to 2 minutes. Remove from heat; stir in bacon, sour cream, hot pepper sauce, and shredded cheese.
Turn tomatoes right side up; sprinkle with salt. Fill tomatoes with spinach mixture. Place in an 8x8x2-inch baking pan. Bake, uncovered, in a 375 degrees F oven for 10 to 15 minutes or until softened. Serve warm. Makes 4 servings.