01 - Preheat your oven to 400°F (200°C) with rack positioned in the center.
02 - Arrange onion slices and carrot chunks evenly across the bottom of a large roasting pan to create a flavorful base for the chicken.
03 - Rub the entire surface of the chicken with olive oil, then season generously with kosher salt, black pepper, and fresh lemon zest, ensuring even coverage.
04 - Fill the chicken cavity with both halved lemons, the halved garlic bulb, and fresh thyme sprigs to infuse flavor from within.
05 - Cross the legs and tie securely together with kitchen twine, then tuck the wing tips underneath the body to promote even cooking.
06 - Place the chicken breast-side up directly on top of the vegetable bed in the roasting pan.
07 - Roast for 1 hour 10 minutes, basting with pan juices once or twice during cooking, until juices run clear and internal temperature reaches 165°F when measured at the thickest part of the thigh.
08 - Transfer the chicken to a cutting board and let rest for 10 minutes to allow juices to redistribute throughout the meat. Carve and serve with pan juices and roasted vegetables.