Preheat oven to 350 F. Take packaged organs out of the fryer chicken if there are any. Rinse chicken under cold water well inside and out. Pat dry with paper towels. Place the whole peeled onion, lemon segments and rosemary inside the cavity of the chicken. Sprinkle salt and pepper on the outside of the chicken. Place chicken in a stainless steel roasting pan and cover the pan bottom with a bit of water (about ¼ inch of water at bottom of pan). Cook in oven, 1-1/2 hrs or until breastbone flesh gives way when prodded with fork. Pour juices from pan over chicken with a ladle every 15 to 20 minutes. If chicken starts to burn on top, cover with a sheet of tinfoil. Serve whole, sliced or jointed, hot or cold. You can use chicken leftovers for sandwiches.