In heavy pan with a lid, saute butter, onions, and garlic until soft and lightly brown. Add spices and fry for 2 to 3 minutes, stirring constantly. Add chicken and brown on all sides. Mix yogurt, coconut milk, and turmeric together and add to chicken. Cover with a tight-fitting lid and simmer for 35-45 minutes until chicken is done and tender. Serve over rice.