Preheat oven to 350F. Mix together melted butter, eggs, buttermilk and cake mix in a bowl until smooth (it will be thick).
Add mixture to pint freezer bag and cut end off.
Spray donut pan with non stick spray and squeeze mixture into pan (barely halfway full).
Bake for about 10 minutes or until donut springs back.
Video
Notes
How to Glaze Donuts
Put on a cooling rack when done. Wait until they are cooled to add any frosting or glaze. You can frost with a tub of frosting and decorate with sprinkles or Melt Chocolate Chips in Microwave and dip top into it, sprinkle and allow to harden