Spray 12-inch skillet with nonstick cooking spray. Heat over medium-high heat until hot. Add beef; cook about 8 minutes or until browned, turning once.
Layer beef, onions, garlic and gingerroot in 3 1/2- to 6-quart slow cooker. In small bowl, combine broth and soy sauce; mix well. Pour over beef.
Cover; cook on low setting for 7 to 9 hours.
About 15 minutes before serving, in small bowl, blend water and cornstarch until smooth. Gradually stir into beef mixture. Stir in bell peppers. Increase heat setting to high; cover and cook an additional 10 to 12 minutes or until slightly thickened. Add tomatoes; cover and cook an additional 3 minutes or just until tomatoes are thoroughly heated.