Cut the chicken into bite-size pieces and mix with the tandoori paste and yoghurt. Leave to marinate in a non-metallic dish for at least a couple of hours (or overnight), stirring occasionally.
Heat the oil or ghee in a deep frying pan, and when it's very hot add the cinnamon, cardamom pods and onion. Fry for about 5-6 minutes until beginning to brown, then add the ginger, garlic, cumin, coriander, turmeric and cayenne pepper.
After the spices have cooked for about a minute, add the chicken with the marinade. Fry for 3-4 minutes, then add the tinned tomatoes, chicken stock or water, garam masala, lemon juice and salt. Bring the curry to a simmer and cook on a low heat for about 10 minutes. Serve straight away with rice or naan bread.