Begin by cutting the chicken thighs into bite-sized pieces and placing them in a large bowl. Sprinkle with salt, garlic powder, sweet paprika, and curry powder, then scoop in the Greek yogurt. Mix well to ensure each piece is coated, then let this marinate for at least 15 minutes at room temperature.

In a large skillet, heat 2 tablespoons of vegetable oil over medium-high heat until shimmering. Add the marinated chicken pieces to the hot oil and sauté for about 8 to 10 minutes, turning occasionally, until the chicken is golden brown and cooked through. Remove the chicken from the skillet and set aside on a plate.

Lower the skillet heat to medium and add 2 tablespoons of butter. Once melted, toss in 3 minced garlic cloves and one finely diced onion. Sauté the mixture for about 3 to 4 minutes until the onion is translucent and fragrant.

Pour in 1 cup of tomato sauce and sprinkle in 1 tablespoon of sugar to balance acidity. Stir well to combine and let it simmer for 2 to 3 minutes. Return the sautéed chicken pieces to the skillet, ensuring they're coated in the tomato base.

Add a pinch of cayenne pepper and 1 tablespoon of garam masala to the skillet along with freshly ground black pepper. Stir everything together and let the mixture simmer gently over low heat for about 10 minutes.

Stir in another tablespoon of butter until melted and creamy. Taste the sauce and adjust seasoning if necessary.

Once everything is combined and beautifully simmered, serve your homemade butter chicken hot with warm naan or fluffy basmati rice.