In a large mixing bowl, combine Greek yogurt, lemon juice, ginger-garlic paste, and your spice blend, stirring until well mixed. Cut the chicken into bite-sized pieces and thoroughly coat with the marinade. Cover the bowl with plastic wrap and refrigerate for at least 1 hour, ideally overnight.

Heat a tablespoon of oil in a large skillet over medium-high heat. Once hot, add the marinated chicken in batches to avoid overcrowding the pan. Sear the chicken for 5-7 minutes until golden brown on all sides. Remove the chicken and set aside.

In the same skillet, reduce heat to medium and add a tablespoon of butter or ghee. Once melted, add finely chopped onions, sautéing until they turn golden. Add minced garlic and ginger, cooking for an additional 1-2 minutes.

Incorporate tomato paste and crushed tomatoes into the skillet, stirring well to combine. Bring the mixture to a simmer on low heat for 10-15 minutes.

Slowly stir in the heavy cream or coconut milk. Add salt and sugar to taste. Continue simmering for an additional 5 minutes until creamy and well-blended.

Return the cooked chicken to the skillet, mixing gently into the sauce. Allow to simmer together for 5 more minutes.

Finish with a splash of lemon juice and fresh cilantro on top. Serve with naan or basmati rice.