Grind all the ingredients under 1st marinade without adding any water.
Grind all the ingredients under 2nd marinade to make a thick paste. Do not add any water.
Marinate the lamb pieces along with the diced onions in the 1st marinade and keep for 1 hour.
Squeeze out the excess moisture if any and marinate the lamb and onion in the 2nd marinade and keep for 2 hours.
Pierce the lamb pieces and onions onto wet bamboo skewers. You can either insert the onion pieces between each piece of lamb or at the ends like I have done.
Grill till the lamb is cooked well and tender. If you think it is getting dry, baste using melted butter.
Serve hot with a sprinkle of chat masala and lemon wedges. I added a side salad and mint-coriander chutney which went well with the lamb skewers.