Roast Lamb Shawarma

PREPARE THE MEAT
2 On the fat side, trim off excess, leaving just a thin layer. On the other side, slice off any thick pockets of fat.
3 Make one inch deep slashes in the thickest parts on the seam side. Flip over and score on the fat side, barely going through the fat layer.
SEASON AND MARINATE
6 Roast the spices in a skillet and grind into a fine powder in a spice grinder. Combine the ground spices with grated ginger, grated garlic, lemon juice, olive oil and salt into a thick paste. Tip: roasting of spices makes the spice blend intense, but it is optional.
7 Pat the lamb dry and coat 2/3 of spice paste onto the seam side, rubbing into the slashes. Spread rest of the marinade on the fat side evenly.
8 Cover and place it in the refrigerator to marinate few hours to [timer minutes=720]overnight[/timer].
ROAST THE LAMB
11 Preheat oven at 350ºF.
12 Let the marinated meat sit at room temperature for [timer minutes=30]30 minutes [/timer]before roasting.
13 Scatter onion slices in the roasting pan and place a rack over that. Transfer the meat, fat side up, over the rack. Pour two cups of water in the base of the pan. Cover and bake for about [timer minutes=90]1½ hours[/timer].
14 Then remove the lid. Baste the lamb with the juices collected in the bottom of the pan.
15 Roast the fat side until golden brown on the top.
16 Flip the lamb meat and place it seam side up. Brush with pan juices and roast until meat has a golden brown crust on this side too. Roasting both sides should take an additional [timer minutes=30]30 to 60 minutes[/timer].
17 It is well done, when the meat is fork tender but don’t roast until it disintegrates. Place a lid ajar and let it rest for about [timer minutes=20]20 minutes[/timer] before cutting. That will retain the juices better and make it firmer.
SLICE THE MEAT
20 Transfer the roasted lamb leg meat to a carving board to slice.
21 Using a slicing knife cut thin slices against the grain. Save the juices from the roasting pan to use for reheating or drizzle on the meat while making sandwiches.
22 Serve with naan, dill rice or couscous, sliced vegetables (cucumber, tomatoes, peppers, onions), tahini sauce (recipe notes below), hot sauce, pickles and tabouli or mast-o musir (yogurt dip).