Place the dry marinade ingredients in a large bowl and mix to blend.
Add the lamb pieces and toss them with the dry spices to coat thoroughly.
Add the remaining wet marinade ingredients and stir to evenly coat the lamb. Cover the bowl and place in the refrigerator to marinate for at least 4 hrs.
Remove lamb from refrigerator 30 mins before cooking. Thread lamb pieces onto wooden skewers with the onion chunks in between pieces.
Grill until lightly charred, 4 minutes per side for medium rare.