1. Wash and cut the chicken into 8 pieces, reserving the back bone for stock if you like, place it in a large bowl.
2. Using the tip of the knife give small jabs to the chicken pieces, so that the marinate goes inside of the chicken.
3. Chop ginger and garlic, set aside.
4. Add yogurt, ginger and garlic, cayenne powder, cardamom powder, clove powder, cumin powder, coriander powder, lemon juice and salt and pepper to taste.
5. Coat the chicken with the marinade, cover it with plastic wrap and let the chicken sit in the marinade for 4 hours or overnight in the refrigerator.
6. Slice the cucumber, and wedge the lemon for garnish.
7. Prepare a hot charcoal fire. When the coals are covered with white ash, push them over to one side of the grill.
8. Replace the grill rack and cover the grill until the rack is hot, about 5 minutes.
9. Arrange the chicken parts bone side down on the hot rack over the coals, cover the grill, and cook for 15 minutes.
10. Turn the chicken and place it opposite the coals, replace the grill cover, and cook until the juices run clear when the meat is pricked with a fork, 10 to 15 minutes more.
11. Place the rice in the center of the serving plate, place the tandoori chicken on top.
12. Place the cucumber slice on the side and garnish with cilantro and lemon wedge.
13. Serve the tandoori chicken with hot naan.