500 g (1 lb) skinless swordfish, boned and cut into bite-sized chunks
2 limes, cut into segments, plus extra to garnish
handful of fresh bay leaves
Mix together the onion, garlic, most of the sumac and the oil in a shallow bowl. Season with pepper, then toss in the swordfish and leave to marinate for 10 minutes.
Thread the fish onto 4 metal skewers, alternating with the lime segments and bay leaves. Cook over a barbecue or under a preheated grill for 2–3 minutes on each side until the swordfish is browned and cooked through. Sprinkle with the remaining sumac and serve immediately, with extra lime wedges to squeeze over.