Brown beef in large pot with green pepper and onion until beef is no longer pink. Drain well. Dissolve bouillon cubes in hot water. Add to beef and stir in tomatoes, chili powder, salt, cumin, garlic powder and pepper. Cover and simmer 30 minutes. Adjust seasonings to taste. Crumble a taco shell (or chips) into each bowl. Add soup and top with grated cheese. A dollop of sour cream is a nice addition!