In a bowl, toss the chicken with salt, garlic powder, sweet paprika, curry powder, and Greek yogurt. Mix until evenly coated and let sit for 15 to 30 minutes.

Heat 2 tablespoons vegetable oil in a large skillet over medium-high heat. Add chicken in a single layer and sear until browned, about 3 to 4 minutes per side.

Transfer seared chicken to a plate.

In the same skillet, add 1 tablespoon butter and the remaining 1 tablespoon oil. Add diced onion and sauté until soft and translucent, about 5 to 6 minutes.

Add minced garlic and cook for 30 seconds until fragrant.

Pour in the tomato sauce and stir in sugar, remaining salt, black pepper, and extra curry powder. Bring to a gentle simmer.

Return the browned chicken to the skillet and stir to coat with sauce. Reduce heat to low and simmer for 10 to 12 minutes.

Stir in the heavy cream and the remaining 2 tablespoons butter until the sauce is glossy and smooth.

Add cayenne pepper if desired, then sprinkle garam masala over the top. Taste and adjust seasoning.

Garnish with chopped parsley, if using. Serve immediately with warm naan and steamed rice.