Prep the chicken: Place the chicken breast-side down. Use kitchen shears to cut along both sides of the backbone and remove it.
Flip the chicken breast-side up and press firmly on the breastbone to flatten. Pat dry with paper towels.
Mix the marinade: In a bowl, combine olive oil, lemon juice, lemon zest, apple cider vinegar, honey, sumac, coriander, garlic, salt, pepper, and chili flakes if using. Taste and adjust salt or honey for balance—tangy with a gentle sweetness is the goal.
Coat the chicken: Rub the marinade all over the chicken, getting under the skin where possible.
Let it sit at room temperature for 20–30 minutes while you prep the quinces.
Prep the quinces: Peel, core, and cut into thick wedges. Toss with a drizzle of olive oil, a pinch of salt, and a bit of honey. Add thyme or rosemary if you like.
Preheat the air fryer: Set to 375°F (190°C) for 5 minutes.
If your air fryer has a rack insert, use it so fat drips below.
Load the basket: Lay the chicken skin-side up. Arrange quince wedges around the edges if there’s space. If not, cook them after the chicken rests, or start them first for 10 minutes to get ahead.
Air fry: Cook at 375°F (190°C) for 25 minutes.
Check the quinces—remove any that are deeply golden and soft. If still firm, leave them in.
Flip and finish: Carefully flip the chicken skin-side down for 5 minutes to render more fat. Flip back skin-side up, brush with a touch of honey and lemon, and cook another 8–12 minutes, until the thickest part of the breast hits 160°F (71°C) and the thigh reaches 175°F (79°C).
Skin should be well-browned and crisp.
Rest: Transfer the chicken to a cutting board and rest 10 minutes. The internal temperature will rise slightly as it rests.
Finish the quinces: If they need more color, run them at 380°F (193°C) for 4–6 minutes until caramelized and tender. Toss with a final drizzle of honey and a squeeze of lemon.
Serve: Carve the chicken into halves or quarters.
Spoon any basket juices over the meat. Serve with the roast quinces and a green salad or couscous.