In a mixing bowl, combine chicken chunks with salt, garlic powder, paprika, curry powder, and Greek yogurt. Mix thoroughly until every piece is coated, then cover and refrigerate for 15-30 minutes.

Heat vegetable oil and 1 tablespoon butter in a large skillet over medium heat. Add minced garlic and diced onion, sautéing for 3-4 minutes until the onion turns translucent and fragrant.

Pour in tomato sauce, sugar, salt, black pepper, heavy cream, cayenne pepper, garam masala, and curry powder. Stir well and bring to a gentle simmer. Reduce heat to low and let the sauce bubble softly for 5-7 minutes, stirring occasionally.

While the sauce simmers, heat a separate pan over medium-high heat. Add the marinated chicken in a single layer and cook for 6-8 minutes, turning occasionally until golden brown on all sides and cooked through to 165°F internal temperature.

Transfer the cooked chicken into the simmering sauce. Add the remaining 2 tablespoons of butter and stir gently to combine. Let everything simmer together for 3-5 minutes.

Taste and adjust seasoning with additional salt or cayenne if needed. Garnish with fresh parsley and serve immediately with warm naan bread and steamed basmati rice.