Preparing :Peel the onions, chop finely or grate, add salt, black pepper and thyme and rub the lamb inside and out with this mixture. Spread the lamb well on the outside with a yogurt and tomato paste mixture. Place an uncovered kettle full of water at the bottom of the tandır, which is preheated and has coal embers at the bottom. Suspend the lamb over tandır so that it does not touch the bottom. Close the lid of tandır and seal it with dough, leaving to cook for about 2 hours. As tandır (an underground brick oven) cannot be readily found everywhere, you can first cook the lamb in a covered large kettle with about 2 cm. water on the bottom over low heat. Then spread it first with the onion - spice and then yogurt- tomato paste mixture and place in a large baking pan. Bake it in oven, adding the cooking liquid of the meat.
Good Apetite.