Take a large resealable freezer bag and put the chicken thighs in it. Using a fine grater grate in the lemon zest. Squeeze the lemons and add the juice. Pour in the olive oil and add the garlic, then add all the remaining ingredients.
Squish everything about together, then seal the bag, place it on a plate or in a dish, and refrigerate for at least 6 hours, or up to 1 day.
When you’re ready to cook, preheat the oven to 220C/200C Fan/Gas 7. Remove the chicken from the fridge and allow it to reach room temperature.
Tip the contents of the freezer bag into a shallow roasting tin – about 44x34x1.5cm and make sure all the chicken thighs are lying flat and not on top of one another before roasting in the hot oven for 30 minutes, by which time they should be cooked through and golden on top.
When the chicken’s more or less cooked, make the sauce simply by combining the yoghurt with the tahini and garlic, stir and salt to taste, and sprinkle with a few pomegranate seeds.
Line a platter or a couple of plates with crisp lettuce, shredded or torn into pieces, and then top with the piping hot chicken, pouring the oily juices over them. Serve with the pittas