Place onion, garlic, ginger, saffron, lime juice, yogurt and the remaining spices in a bowl. Stir to combine.
Place the hens in a baking dish and rub the entire hen, including the cavity with the marinade. Cover the hens and let marinate in the refrigerator for at least 4 hours and up to 24 hours.
Preheat the grill to high. Skewer the hens on the rotisserie and grill for approximately 1 1/4 hours or until cooked through.
Place the sliced onions in a bowl of ice water, cover and refrigerate while the hens are grilling. Right before serving, remove the onions from the water and pat dry. Half the hens and serve with onion slices, cilantro sprigs and lime wedges.