Place lamb meat into a large nonmetallic bowl. Grind the coriander seed in a mortar and pestle, and rub into the meat. Pour orange juice and orange liqueur over meat, and mix in minced chile pepper and chopped orange. Cover, and refrigerate for 24 hours. Turn the meat over every couple of hours.
Preheat grill for medium heat. Remove the lamb and orange pieces from marinade, and transfer marinade to a small saucepan. Set marinade aside. Thread the cubes of lamb on skewers, alternating with pieces of orange, and starting and finishing with a piece of orange.
Place saucepan with marinade on the grill, and bring to the boil. Continue boiling until reduced to a sticky but fluid sauce.
Once the marinade has come to the boil, place the skewers on the grill. Cook slowly until slightly charred, and cooked to your preference. Transfer skewers to a warm dish, and cover for 5 minutes. Serve with the orange sauce, garnished with sprigs of fresh cilantro.