4 servings (serving size: 1 quesadilla and 3 tablespoons salsa)
Combine first 3 ingredients in a small bowl; stir until blended.
Place 1/4 cup chopped chicken over half of 1 tortilla. Sprinkle with 3 tablespoons cheese and 1 tablespoon onion mixture; fold in half. Repeat procedure with the remaining tortillas, chicken, cheese, and onion mixture.
Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Place 2 quesadillas in pan. Cook 2 minutes on each side or until lightly browned. Repeat procedure with remaining quesadillas. Cut each quesadilla in half. Serve with salsa.