In a small bowl, mix together the melted butter, Parmesan cheese, garlic, and onion powder.
Place the thighs in a baking dish and pour the mixture on top the thighs.
Cover the baking dish with plastic wrap and refrigerate for 1 hour.
Preheat the oven to 400°F.
Bake the chicken thighs until they reach an internal temperature of 145°F.
Serving Size 1
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.