Grate ½ tsp of rind from the orange. Cut unpeeled orange into wedges then cut wedges in half. Combine orange rind, yogurt and Patak's Madras Paste into a large bowl. Add the beef cubes and allow to marinate in the refrigerator, covered for ½ hour. Thread the beef cubes onto skewers alternating with orange, green pepper and onion. Cook over low coals or under a moderate grill 4-5 inches from heat for 10-15 minutes, turning occasionally.