Combine all the ingredients in the tandoori marinade except the lemon. The lemon goes in at the end. Lemon is acidic. It "cooks" the chicken as it sits. You don't want this.
Cut the chicken into 10 pieces. Quarter the chicken. Cut the drumstick from the thigh. Cut the wings off the breasts. Halve the breasts. Remove the skin from the breasts, drumsticks and thighs. Leave the skin on the wings.
Combine tandoori marinade with chicken. Refrigerate for at least 1 hour and up to 12 hours.
Add the lemon juice right before you light the grill.
Light your grill. Build a two zone fire if using charcoal. Turn your gas grill to max on all the burners except one. You want high, indirect heat. If you can get your grill over 500F that's perfect.
If you have a kamodo grill experiment with higher temperatures. I'm not saying go to 800F and walk away though. The hotter the grill, the more you have to pay attention. Gets pretty tricky above 600F.
Different chicken pieces cook at different rates. Keep that in mind. Start your thighs first. Breasts and drumsticks next. Wings last. And don't just check one piece with your thermometer. Move it around. And pull your chicken pieces when they are ready. Perfect tandoori chicken means all the pieces are cooked perfectly.
Grill the chicken over indirect heat until almost done - around 20-25 minutes. This depends on how hot your grill is so use your instant read thermometer and cook to about 155F. Always use an instant read thermometer.
Move the chicken over direct (high) heat and grill an additional 2-4 minutes, turning every minute. You want a bit of char but you don't want it to burn or dry out.
Brush with a bit of ghee if using. Serve garnished with a bit of cilantro and thinly sliced white onion or shallot. A bit of raita works nicely too.