Cook bacon in a heavy skillet over medium heat until partially cooked. Drain well on paper towels; set aside.
Cut a thin slice from bottom of each tomato half so it will sit flat; place tomato halves in a shallow roasting pan. Broil 6 inches from heating element 10 minutes. Remove from heat, and place a slice of cheese on each tomato half; top with bacon pieces. Return to oven and broil an additional minute or until cheese melts and bacon is cooked. Serve immediately.