½ cup barbecue sauce (homemade or your favorite brand)
In a large bowl whisk together the buttermilk, cayenne pepper, ½ teaspoon salt, and ½ teaspoon pepper. Place chicken breasts between plastic wrap and using a mallet pound chicken down to about ½ inch. Place chicken in a large food grade ziplock bag, pour in the buttermilk mixture, and using your hands on the outside of the bag work the buttermilk around the chicken; marinate in the refrigerator for 30 minutes.
Prepare grill on medium-high heat.
Remove chicken from the marinade; letting any excess marinade drip off the chicken. Pat chicken dry using paper toweling. Coat chicken breasts on both sides with olive oil and lightly salt both sides. Grill chicken for 2 to 4 minutes or until grill marks form, flip chicken and grill for another 3 to 4 minutes, coat with barbecue sauce, flip chicken to coat the other side. Continue grilling until an instant-read thermometer reads 160F. (if you have sauce left over flip chicken again to thicken the coating)
Place chicken on a serving platter, tent lightly with aluminum foil and let rest 5 to 10 minutes, and serve.