In a bowl, toss chicken pieces with 1 tablespoon olive oil, 1 tablespoon sumac, cumin, coriander, paprika, cinnamon, salt, and pepper. Let marinate for 15 minutes.

While chicken marinates, heat remaining olive oil in a large skillet over medium heat. Add sliced onions and cook, stirring occasionally, until soft and lightly caramelized—about 15–18 minutes.

Push onions to the skillet edge, add marinated chicken to center, and cook for 5–6 minutes until lightly browned. Flip and sauté another 5 minutes until chicken is cooked through.

Sprinkle remaining 1 tablespoon sumac over the chicken-onion mixture and stir to combine. Taste and adjust seasoning.

Warm flatbreads briefly in a dry skillet or oven until pliable.

Divide the chicken and onion mixture evenly among flatbreads. Add a sprinkle of toasted pine nuts and fresh herbs if using.

Roll each flatbread tightly, tucking in the ends to form neat rolls.

Serve warm, either whole or sliced in half, garnished with extra sumac or herbs.