Using your fingers, gently loosen the skin from the chicken breasts, thighs and drumsticks; try not to tear the skin. Season the cavity of the chicken with salt and pepper and put the chicken in a roasting pan. Using a small spoon, pour all but 1 tablespoon of the seasoning mixture under the skin of the chicken, rubbing it into the breasts, thighs and drumsticks. Rub the butter under the skin of the breast meat. Rub the remaining 1 tablespoon of the seasoned oil all over the chicken and season it with salt. Put the reserved lemon halves in the cavity of the chicken and tie the legs together with twine.