In a medium bowl, combine chicken pieces, salt, garlic powder, sweet paprika, curry powder, and Greek yogurt. Mix well until fully coated. Marinate for at least 15 minutes.

Heat 3 tablespoons of vegetable oil in a large skillet over medium-high heat. Cook the marinated chicken for 8 to 10 minutes, stirring occasionally, until golden brown and cooked through. Remove chicken and set aside, leaving the oil in the pan.

Reduce heat to medium. Add 1 tablespoon of butter and scrape up any browned bits. Add minced garlic and diced onion with a pinch of salt. Saute for 3 to 4 minutes until soft and translucent.

Stir in tomato sauce and sugar. Simmer for 2 to 3 minutes. Return chicken to the skillet and stir to combine. Pour in heavy cream and stir until the sauce turns a rich orange color.

Add cayenne pepper if using, garam masala, second addition of curry powder, and black pepper. Reduce heat to low and simmer for 10 minutes until the sauce thickens slightly.

Remove from heat and stir in the remaining 2 tablespoons of cold butter until melted and the sauce is silky. Garnish with fresh parsley and serve hot over rice with naan.