In a large mixing bowl, combine the plain yogurt, lemon juice, ground cumin, ground cinnamon, Kashmiri chili powder, tandoori masala, black pepper, minced ginger, minced garlic, and salt. Mix well. Add the chicken thighs and stir until the chicken is well coated. Cover and let it marinate in the refrigerator for at least 30 minutes, or up to overnight for maximum flavor.
Heat a large skillet or Dutch oven over medium heat. Add 2 tablespoons of butter. Once melted, add the marinated chicken in batches, being careful not to overcrowd the pan. Sear the chicken for about 5-7 minutes, or until golden brown. Remove the chicken from the pan and set aside.
In the same skillet, add another minced clove of garlic and sauté for about 30 seconds until fragrant. Add the second teaspoon of Kashmiri chili powder, ground cumin, paprika, and garam masala. Stir well to combine, allowing the spices to toast for a minute.
Pour in the tomato sauce (or Passata) and stir to incorporate with the spices. Allow the mixture to simmer for about 5 minutes. Then, slowly stir in the heavy cream, mixing until smooth. Season with salt to taste.
Return the seared chicken to the skillet, stirring to coat the pieces in the sauce. Let it simmer for an additional 10-15 minutes, allowing the flavors to meld and the chicken to cook through.
Once the chicken is cooked through and the sauce is thickened, remove from heat. Garnish with fresh cilantro. Serve your Easy Chicken Tikka Masala over a bed of cooked rice and alongside warm naan bread for dipping.
