Roast Chicken with Sumac and Lemon

My good friend, Luis Calvo Alonso brought me a packet of the exotic sumac spice from Istanbul. I decided to adapt a recipe from Yotam Ottolenghi. I do not have za'atar, which is a blend of spices usually consisting of thyme, sumac, oregano and toasted sesame seed.  I made my own blend with ajwain (a thyme flavored seed), sumac and white sesame seeds instead. The chicken is quartered and seasoned overnight, before it is roasted together with the marinate in a casserole at 200 deg C.  Before serving, it is garnished with roasted pine nuts, parsley and a drizzle of olive oil.

Ingredients
1 large free-range chicken, divied into quarters
2 red onions, thinly sliced
2 garlic cloves, crushed
4 tablespoons olive oil, plus extra for drizzling
1 1/2 teaspoons ground allspice
1 teaspoon ground cinnamon
1 tablespoon sumac
1 lemon, thinly sliced
200ml chicken stock
1 1/2 teaspoons salt
1 teaspoon ground black pepper
2 tablespoons za’atar
20g butter
50g pine nuts
4 tablespoons chopped flat leaf parsley