Between pieces of plastic wrap or waxed paper, place each chicken breast smooth side down; gently pound with flat side of meat mallet or rolling pin until about 1/2 inch thick. Sprinkle chicken with 1/2 teaspoon salt and 1/4 teaspoon pepper.
In 12-inch nonstick skillet, heat 1 tablespoon extra-virgin olive oil over medium-high heat. Cook chicken breasts in oil 6 to 8 minutes, turning once, until brown.
Add cooking sauce, spinach and lemon peel to skillet; stir to blend. Spoon sauce mixture over chicken in skillet. Reduce heat to medium-low; simmer uncovered 12 to 15 minutes or until chicken is no longer pink in center. Sprinkle with bell pepper.