Preheat oven to 425°F. Lightly grease donut baking pan; set aside.

In a medium bowl, add all of the dry ingredients (cake flour, granulated sugar, cocoa powder, baking powder and salt); stir until well combined.

In a separate bowl, whisk together the egg, buttermilk, vanilla extract, melted butter, heavy cream and red food coloring. (Tip: Add a small amount of food coloring at first and then continue adding more until the batter turns bright red. You can always add more food coloring, but you can't take it out!)

Add the liquid ingredients to the dry ingredients; stir until just mixed.

Spoon or pipe the batter into the prepared pan. (Tip: Fill each well about half full of batter.)

Bake for 12-14 minutes, or until donuts just begin to turn light brown on top.

Let donuts cool in the pan.

Place powdered sugar in paper bag. Once donuts have cooled, shake donuts (one at a time) in the bag with the powdered sugar until well coated. Tap off any excess powdered sugar. Repeat with remaining doughnuts. Serve immediately. (Note: If you plan on serving these doughnuts later, store them uncoated in an air-tight container. Shake them in powdered sugar just before serving.)