Heat a grill pan or large nonstick skillet over medium-high heat. Coat pan with cooking spray. Sprinkle chicken with pepper and salt. Coat chicken with cooking spray, and add to pan. Cook 3 to 4 minutes on each side or until done.
Divide spinach evenly on each of 4 serving plates; drizzle evenly with Pomegranate Vinaigrette. Arrange chicken, onion, and blueberries evenly over spinach. Sprinkle evenly with cheese.
Antioxidant-rich pomegranate juice has found a place in a healthful diet that stretches beyond a quick cup of juice with breakfast. Pomegranate juice has a rich and tangy flavor, which makes it an ideal ingredient to use in simple salad dressings and pan sauces with short ingredient lists.