1.Combine the water and burghul in small bowl; stand 30 minutes. Drain; squeeze burghul with hands to remove excess water.
2.Meanwhile, blend or process chickpeas, yogurt, rind and juice until hummus is smooth.
3.Combine burghul in large bowl with onion, tomato, cucumber and herbs; add extra juice, toss gently until tabbouleh is combined.
4.Toss lamb in sumac; cook, in batches, on heated lightly oiled grill plate (or grill or barbecue) until browned both sides and cooked as desired.
5.Just before serving, spread hummus equally over half of each slice of the bread, top with equal amounts of lamb and tabbouleh; roll to enclose filling. Cut into pieces, if desired, to serve.