01 - Preheat oven to 400°F.
02 - Place onion slices and carrot chunks in the bottom of a large roasting pan to create a bed for the chicken.
03 - Rub the chicken all over with olive oil, salt, pepper, and lemon zest.
04 - Stuff the chicken cavity with both halved lemons, halved garlic bulb, and fresh thyme sprigs.
05 - Tie the legs together with kitchen twine and tuck wings under the body.
06 - Place the chicken breast-side up on top of the vegetables in the roasting pan.
07 - Roast in the preheated oven for 1 hour 10 minutes, basting once or twice, until the juices run clear and the internal temperature reaches 165°F.
08 - Let the chicken rest for 10 minutes before carving. Serve with pan juices and roasted vegetables if desired.