1. Cook the elbow macaroni according to the directions on the box, and be sure to drain well.
2. Meanwhile, put beef in heavy skillet, chop up and brown over medium heat, and drain if necessary.
3. Sprinkle chili powder into browned meat and stir.
4. Add the chili beef soup and diced tomatoes (with liquid) to the skillet, stir and continue cooking over medium heat for about 10 minutes, stirring occasionally.
5. Stir in the cooked elbow macaroni noodles, and heat through, about 5 minutes.
6. Sprinkle the cheese over the top and cook 3 or 4 minutes, without stirring, until the cheese melts.