Preheat oven to 350 degrees F (175 degrees C). Lightly grease a baking sheet. Heat a cast iron skillet over high heat for 5 minutes until it is smoking hot. Mix together the paprika, salt, cayenne, cumin, thyme, white pepper, and onion powder. Oil the chicken breasts with cooking spray on both sides, then coat the chicken breasts evenly with the spice mixture. Place the chicken in the hot pan, and cook for 1 minute. Turn, and cook 1 minute on other side. Place the breasts on the prepared baking sheet. Bake in the preheated oven until no longer pink in the center and the juices run clear, about 5 minutes.