Mix all spices together.
Whisk yogurt, tikka masala, salt, garlic and lemon juice together in a bowl.
Toss the chicken with the yogurt mix. Marinate for 8 to 10 hours in the fridge.
Take the chicken out of the marinade and remove excess marinade by lightly dabbing the chicken with a paper towel. Thread the chicken onto skewers and grill.
In a Dutch oven, melt the butter.
Add the onion and cook until soft (5 to 7 minutes).
Add the remaining tikka masala and garlic and cook for about a minute. Stir in the tomato paste.
Add the tomatoes, the cream and the salt. Add chicken to the sauce, heat everything through, then serve with rice or naan. Sprinkle chopped cilantro on (optional).
