In small bowl, stir together broth, water and cornstarch until smooth; set aside.
In 10-inch skillet over medium heat, in hot oil, cook garlic, parsley, lemon peel and red pepper 1 minute, stirring constantly. Add shrimp and lemon juice. Cook until shrimp turn pink and opaque, stirring constantly.
Gradually add broth mixture to skillet. Cook until mixture boils and thickens, stirring constantly. Toss with spaghetti. 4 servings.