- 1 whole chicken (3 1/2 to 4 pounds), patted dry
- Coarse salt and ground pepper
- 1 large red onion, cut into 1/2-inch wedges, root end left intact
- 1 medium celery root (about 1 pound), peeled and cut into 1/2-inch wedges
- 1/4 to 1/2 teaspoon red-pepper flakes
- 4 teaspoons lemon zest, plus 4 teaspoons lemon juice
- Preheat oven to 425 degrees. Season chicken inside and out with salt and pepper. Tuck wing tips underneath chicken and tie legs together with kitchen twine. Place on a rimmed baking sheet and roast 20 minutes.
- Remove sheet from oven and arrange onion and celery root around chicken, turning to coat with drippings. Top vegetables with red-pepper flakes and season with salt and pepper. Roast until vegetables are tender and juices run clear when chicken is pierced between breast and leg (an instant-read thermometer should read 165 degrees when inserted into the thickest part of a thigh, avoiding bone), about 30 minutes, flipping vegetables halfway through. Let chicken rest 10 minutes before carving. To serve, sprinkle chicken and vegetables with lemon zest and juice.
Lemon Lesson: If you're not using peeled celery root right away, keep it in a bowl of cold water with a squeezed lemon. The acid will prevent the white flesh from browning.