01 - Whisk together olive oil, zaatar, sumac, lemon zest, lemon juice, minced garlic, kosher salt, and black pepper in a small bowl until thoroughly combined.
02 - Gently lift the skin over the chicken breast area and rub half of the marinade directly under the skin, ensuring even coverage over the meat.
03 - Rub the remaining marinade over the entire surface of the chicken, coating all sides evenly for maximum flavor penetration.
04 - Place lemon slices and onion rings inside the chicken cavity to infuse additional moisture and aroma during roasting.
05 - Arrange remaining onion rings, carrot chunks, and lemon slices in a single layer at the bottom of a roasting pan to create a vegetable bed.
06 - Set the chicken breast side up on top of the vegetable bed, ensuring it sits stable and centered in the pan.
07 - Let the chicken rest at room temperature for 30 minutes to absorb flavors, or cover and refrigerate for up to 8 hours for deeper flavor penetration. Bring to room temperature before roasting if refrigerated.
08 - Preheat the oven to 400°F for optimal roasting temperature.
09 - Place the roasting pan in the center of the oven and roast for 1 hour to 1 hour 15 minutes, until juices run clear and an instant-read thermometer inserted into the thickest part of the thigh reaches 165°F.
10 - Remove the chicken from the oven and let it rest for 10 minutes before carving to allow juices to redistribute throughout the meat.