To prepare sauce, melt butter in a medium saucepan over medium heat. Gradually add flour, stirring with a whisk; cook 1 minute, stirring constantly. Gradually add milk, stirring with a whisk; bring to a boil, stirring constantly. Reduce heat, and simmer 2 minutes, stirring constantly. Add cheddar and next 7 ingredients (through red pepper), stirring until cheeses melt. Remove from heat.
Arrange 2 toast halves in the bottom of each of 6 gratin dishes or ovenproof plates. Arrange 2 ounces turkey over each serving. Top each serving with about 1/3 cup sauce, 2 tomato slices, and 1 teaspoon Parmesan. Broil for 2 minutes or until bubbly. Sprinkle each serving with about 1 tablespoon bacon.