Partially freeze steak to firm to meat. Slice diagonally across the grain into very thin strips. Mix cornstarch, sugar and ginger. Stir in soy sauce. Pour mixture over meat. Stir. Cut green peppers into thin strips and cut tomatoes into wedges.
Quickly brown beef strips, 1/3 at a time in hot oil and remove from pan. Reduce heat. Add green pepper, garlic and water to pan. Cook until green pepper is tender crisp, 5 to 6 minutes. Stir in meat and tomatoes. Heat through. Makes 4 servings.