In a 4-quart kettle or Dutch oven, combine 2 quarts water and the meat. Bring to boiling. Skim off all foam.
Add carrots, onion, undrained tomatoes, and soup mix. Return to boiling. Reduce heat. Cover; simmer about 2 hours or until the meat is very tender.
Remove and discard onion. Remove meat. Add desired vegetables to soup. Return to boiling. Cover and simmer for 20 minutes more.
When meat is cool enough to handle, cut into bite-size pieces. Return meat to pan; heat through. Skim off fat before serving. Makes 6 to 8 servings.