Preparation Set strainer over large bowl. Line strainer with 2 layers of cheesecloth (do not let strainer touch bottom of bowl). Spoon yogurt into strainer. Let stand at room temperature 1 hour (liquid will drain out and yogurt will thicken; discard liquid). Mix yogurt, garlic and lemon juice in small bowl. Season to taste with salt. Rub cumin and coriander over lamb pieces. Thread lamb onto 6 metal skewers. (Yogurt and lamb can be prepared 4 hours ahead. Cover separately and chill.) Combine 1 cup water and 1/4 teaspoon salt in medium saucepan. Bring to boil. Add couscous. Remove from heat. Cover; let stand until liquid is absorbed, about 5 minutes. Transfer couscous to large bowl; fluff with fork. Cool to room temperature. Stir in chopped cucumber, tomato, onion, olive oil and fresh dill. Season with salt and pepper. Prepare barbecue (medium-high heat). Grill lamb to desired doneness, turning frequently, about 10 minutes for medium-rare. Transfer to platter. Sprinkle with salt. Grill pitas until heated through and lightly toasted, about 1 minute per side. Place 1 pita on each of 6 plates. Spread yogurt mixture evenly over pitas. Spoon couscous down center of pitas. Slide lamb off skewers onto couscous.
Preparation Set strainer over large bowl. Line strainer with 2 layers of cheesecloth (do not let strainer touch bottom of bowl). Spoon yogurt into strainer. Let stand at room temperature 1 hour (liquid will drain out and yogurt will thicken; discard liquid). Mix yogurt, garlic and lemon juice in small bowl. Season to taste with salt. Rub cumin and coriander over lamb pieces. Thread lamb onto 6 metal skewers. (Yogurt and lamb can be prepared 4 hours ahead. Cover separately and chill.) Combine 1 cup water and 1/4 teaspoon salt in medium saucepan. Bring to boil. Add couscous. Remove from heat. Cover; let stand until liquid is absorbed, about 5 minutes. Transfer couscous to large bowl; fluff with fork. Cool to room temperature. Stir in chopped cucumber, tomato, onion, olive oil and fresh dill. Season with salt and pepper. Prepare barbecue (medium-high heat). Grill lamb to desired doneness, turning frequently, about 10 minutes for medium-rare. Transfer to platter. Sprinkle with salt. Grill pitas until heated through and lightly toasted, about 1 minute per side. Place 1 pita on each of 6 plates. Spread yogurt mixture evenly over pitas. Spoon couscous down center of pitas. Slide lamb off skewers onto couscous.