01 - Combine olive oil, zaatar, sumac, lemon zest, lemon juice, minced garlic, kosher salt, and black pepper in a small bowl. Whisk thoroughly until all ingredients are fully incorporated into a smooth paste.
02 - Carefully lift the skin covering the breast area by sliding your fingers between the skin and meat. Spread half of the marinade evenly beneath the skin, covering as much surface area as possible for maximum flavor penetration.
03 - Rub the remaining marinade generously over the entire exterior surface of the chicken, ensuring complete coverage of all exposed skin and cavity areas.
04 - Arrange the red onion rings, carrot chunks, and lemon slices in a single layer at the bottom of a roasting pan to create a natural roasting rack.
05 - Place the seasoned chicken directly on top of the vegetable bed, positioning it breast-side up for even cooking and optimal browning.
06 - Allow the seasoned chicken to rest at room temperature for 30 minutes before cooking. For enhanced flavor depth, refrigerate for up to 8 hours, then bring to room temperature for 30 minutes prior to roasting.
07 - Set oven temperature to 400°F and allow it to fully preheat for at least 15 minutes before inserting the chicken.
08 - Place the roasting pan on the center rack and roast for 60 to 75 minutes. The chicken is properly cooked when juices run clear and an instant-read thermometer inserted into the thickest portion of the thigh registers 165°F.
09 - Remove the chicken from the oven and allow it to rest for 10 minutes. This resting period redistributes juices throughout the meat, ensuring moist and tender results when carved.
10 - Transfer the chicken to a carving board and slice into serving pieces. Plate with the roasted vegetables and drizzle with the flavorful pan juices from the bottom of the roasting pan.