Preheat oven to 200°C (400°F). In a small bowl, combine 2 tablespoons sumac, cumin, allspice, cinnamon, salt, pepper, and 3 tablespoons olive oil to form a paste.

Pat chicken dry with paper towels and rub the spice paste all over, including under the skin where possible. Place on a roasting tray.

Roast chicken for 55-65 minutes until the skin is golden and crispy, and internal temperature reaches 75°C (165°F) when measured at the thickest part of the thigh.

While chicken roasts, heat remaining 3 tablespoons olive oil in a large pan over medium heat. Add sliced onions and cook for 25-30 minutes, stirring occasionally, until deeply caramelized and golden brown.

Stir remaining 2 tablespoons sumac into the caramelized onions and cook for another 2 minutes. Season with salt to taste.

Toast pine nuts in a dry pan over medium-low heat for 2-3 minutes until golden, watching carefully to prevent burning.

Warm flatbreads in the oven for 3-4 minutes. Spread caramelized sumac onions generously over each flatbread.

Rest the cooked chicken for 10 minutes, then carve or shred into pieces. Arrange chicken over the onion-topped flatbreads.

Garnish with toasted pine nuts and fresh parsley. Serve immediately with lemon wedges on the side.