If you're using wooden skewers, be sure to soak them in cold water for one hour prior to skewering the chicken, so that they don't burn on your grill. For metal skewers, lightly grease them with olive oil or cooking spray. Preheat and clean your grill.
Combine the onions, lemon juice, garlic, olive oil, paprika, turmeric, garam masala, coriander, cayenne, salt, and greek yogurt in the cup that came with your hand mixer, or in a blender or a food processor. Puree until smooth.
Trim off the small piece of tendon that may be on some of your chicken tenderloins and then cut into 1" bite-sized pieces.
Skewer the chicken, and then coat with kebab sauce. Allow them to marinade for 15-30 minutes before grilling.
Grill over direct high heat (450º-550º F) for 10-12 minutes, turning 2 or 3 times. Be sure to keep the lid closed as much as possible.
Serve on the skewer, or slide them off with a fork (metal skewers tend to get too hot for serving). Garnish with cilantro before serving.