Fry bacon on pan made of aluminum foil or on griddle over hot coals till partially done but not crisp.
Blend brown sugar, mustard, and salt.
Make a vertical cut down center of tomatoes, about 2/3 of the way through.
Spread cut edges with mustard mixture.
Crisscross 2 bacon slices.
Place tomato on bacon where slices cross; bring strips to top of tomato and secure with toothpicks.
Place tomatoes on aluminum foil.
Cook covered over coals till tomatoes are hot.