Place the cilantro, small onion, garlic, chili, ginger, and salt with 3 tablespoons of the oil in a food processor fitted with a metal blade. Process until a paste is formed. Transfer to a large bowl. Put 2 tablespoons of the paste in a small bowl and stir in the lime juice to make the cilantro sauce. Cover and set aside. Stir the curry powder into the rest of the paste. Add the steak and coat well. Cover and marinate at room temperature for 20 minutes. Cut the red onion into 6 wedges and separate each wedge into 2 layers. Thread the beef and onion chunks onto eight 9-inch skewers. Brush a grill pan with the remaining oil. Preheat grill pan, then grill the kebabs for 8 to 10 minutes, turning the skewers every 2 minutes. Serve with the cilantro sauce, chutney, and naan, if desired.