1. Preheat oven to 450°. Rinse chicken, then pat dry with paper towels. Put chicken in a large cast-iron skillet or roasting pan, then squeeze lemon over chicken to cover all surfaces, inside and out, with juice. Put squeezed lemon halves, several sprigs each of rosemary and thyme, and garlic into cavity of the bird. Tie legs together with kitchen string, then rub butter all over chicken. Season liberally with salt and pepper.

2. Arrange onions, potatoes, carrots, and parsnips around chicken. Brush vegetables with a little olive oil and season to taste with salt and pepper.

3. Roast in the oven for 15 minutes, then baste chicken and vegetables with pan juices. Reduce temperature to 375° and continue to roast, basting occasionally, until skin is crisp and golden, about 45 minutes more.

4. Turn off heat and allow chicken to rest in the oven, with the oven door ajar, for about 15 minutes before carving. Garnish with additional fresh rosemary and thyme sprigs, if you like.