Cajun Oven-Fried Chicken

In large bowl, place chicken and buttermilk; toss to coat. Refrigerate at least 30 minutes, but no longer than 8 hours. Heat oven to 450 °F. Place ovenproof rack on top of rimmed cookie sheet; spray both with cooking spray. Set aside. Place egg whites and bread crumbs in two separate shallow dishes or pie plates. Transfer chicken to large plate, letting buttermilk drip back into bowl. Discard buttermilk. Pat chicken dry with paper towels. Rub Cajun seasoning on both sides of chicken. Dip chicken into egg whites, letting excess drip back into dish. Coat chicken in bread crumbs, pressing to adhere. Lightly spray both sides of chicken pieces with cooking spray; place on rack. Bake 25 to 30 minutes, turning once halfway through cooking, until lightly browned and juice of chicken is clear when center of thickest part is cut (165 °F). If desired, broil 6 inches from heating element 30 seconds to 1 minute to thoroughly brown and crisp the crust.