Stir salt into buttermilk. Remove wingtips from chicken. Place chicken in 1 gallon ziplock back and add buttermilk. Seal the back and thoroughly coat the chicken. Place in refrigerator for 12-24 hours, turning the chicken occassionally.
Remove chicken from the refrigerator 1 hour before cooking. Heat the over to 425°F with the rack in the center position.
Remove the chicken from the bag and scrape buttermilk off. Tie the legs togeter and place in 10" cast iron skillet with legs pointing to the back of the pan. Place the pan in the over with thelegs pointing to the rear left corner of the oven.
After 25 minutes, reduce the heat to 400°s; and continue roasting for 15 minutes.
Move the pan so the legs are pointeed to the right rear corner of the over and cook for another 35-40 minutes. The chicken should be browned all over and juices run clear and the juices run clear when a knife is inserted between the leg and thigh.
Remove to a platter and let rest for 10 minutes before serving.