In a bowl, combine chicken thighs with salt, garlic powder, paprika, curry powder, and Greek yogurt. Mix well and let marinate for 15 minutes.

Heat a large skillet over medium-high heat and add half the butter and a drizzle of oil. Once melted, sear the marinated chicken for 4-5 minutes, then set aside.

In the same skillet, reduce heat to medium, add remaining butter, and sauté diced onion and minced garlic until soft, about 3-4 minutes.

Stir in the tomato sauce, sugar, salt, black pepper, curry powder, and optional cayenne. Simmer for about 5 minutes.

Gradually pour in the heavy cream, stirring continuously until the sauce is smooth. Simmer on low for 5-7 minutes.

Return the seared chicken and juices back into the sauce, add garam masala, and simmer for an additional 8-10 minutes.

Garnish with fresh parsley or cilantro and serve warm over basmati rice or with naan.