1. Spray Dutch oven with cooking spray. Heat over medium-high heat until hot. Add beef and onion. Cook and stir 5 minutes or until beef is browned.
2. Add vegetables, water, tomatoes with juice, celery, bouillon cube and pepper. Bring to a boil. Whisk together beef broth and flour until smooth, add to beef mixture, stirring constantly. Return mixture to a boil. Reduce heat to low. Cover and simmer 15 minutes, stirring frequently.
Note: If time permits, allow the soup to simmer an additional 30 minutes. The flavors just get better and better!