Preheat oven to 375 degrees.
Combine flour, baking soda, baking powder, and salt in a bowl.
In separate bowl combine melted butter, milk, sour cream, egg, and maple syrup. Blend with mixer.
Add in flour mixture and blend into wet ingredients until smooth.
Pour and spread cornbread mixture into a seasoned 10-inch cast iron skillet (or comparably sized dish coated with cooking spray or melted coconut oil).
Bake for about 20 minutes or until edges brown and a toothpick inserted comes out clean. Keep in mind a smaller baking dish may require extra cooking time.