Cook bacon in a heavy saucepan until crisp, reserving drippings in pan. Gradually add broth and salt, and bring to a boil.
Stir in grits and diced tomatoes; return to a boil, stirring often. Reduce heat; simmer, stirring often, 15 to 20 minutes.
Stir in cheese; cover and let stand 5 minutes or until cheese melts. Stir until blended.