Marinate the Chicken: In a medium bowl, combine the chicken, 1 teaspoon salt, garlic powder, sweet paprika, 1/2 teaspoon curry powder, and Greek yogurt. Mix well to coat the chicken. Let it marinate for at least 15 minutes.

Cook the Chicken: Heat 3 tablespoons of oil in a large skillet over medium-high heat. Add the marinated chicken and cook for 8-10 minutes, stirring occasionally, until golden brown and cooked through. Remove the chicken from the skillet and set aside.

Prepare Sauce Base: Reduce the heat to medium. Add 1 tablespoon of butter to the skillet. Add the minced garlic and diced onion, along with a pinch of salt. Sauté until the onion is translucent and fragrant.

Build the Sauce: Stir in the tomato sauce and sugar. Let it simmer for 2-3 minutes before adding the cooked chicken back into the skillet. Mix well, then pour in the heavy cream.

Season and Simmer: Add the cayenne pepper (if using), garam masala, 1/2 teaspoon curry powder, and black pepper. Let the sauce simmer on low heat for 10 minutes to allow the flavors to meld. Add the rest of the salt to taste.

Finish with Butter: Stir in the remaining 2 tablespoons of cold butter and let it melt into the sauce for a silky finish. Sprinkle with chopped parsley if desired.

Serve and Enjoy: Serve hot with naan bread and steamed rice.