On a work surface, with a chef’s knife or kitchen scissors, cut out the backbone of the chicken. Turn the chicken over and cut it in half. Transfer to a large glass dish. Sprinkle the salt and garlic powder over the chicken skin. Rub the chicken halves all over with the cut side of the lemon. Coat well with ½ cup (125 ml) of the ranch dressing. Cover and refrigerate for 12 hours.