Prick the chicken pieces with a fork all over. Apply the tenderiser to the chicken pieces and let it stand for an hour or so.
Take a wide and deep bowl about 12 2 inches wide and deep enough to hold all the chicken pieces.
Add the yoghurt plus one-cup water or the buttermilk with no water into the bowl.
Add all the spices from nos. 3 through 8 into the bowl and stir to form a homogeneous mixture.
Now add the chicken pieces into the mixture, so that they are all covered with the paste/mixture.
Cover the bowl with a lid and let it stand for 6 hours.
If you plan to marinade for 12-15 hours, put it in the refrigerator.
The more time it is marinated, the better it will absorb the spices and the tastier it will be.
When you are ready to grill the chicken, apply melted butter to the the chicken pieces with a brush or spoon all over and you are ready to grill the chicken on the barbecue in the normal fashion.
Turn over the chicken pieces when they look brownish red in colour or darker if you prefer it well done.
Slice finely onion into rings, add some salt and lemon juice to it, to be served as a salad with the tandoori chicken.
Lemon juice sprinkled on the cooked pieces also adds to the flavour, if you wish.