Preheat your oven to 350°F (175°C). Lightly grease a donut pan and set it aside.
In a large mixing bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt until well combined.
In a separate bowl, whisk together the buttermilk, egg, oil, maple syrup (or sugar), vanilla extract, red food coloring, and apple cider vinegar until smooth.
Gently fold the wet ingredients into the dry ingredients, stirring until just combined. Be careful not to overmix.
Transfer the batter into a piping bag or a large zip-top bag with a corner snipped off. Pipe the batter evenly into the prepared donut pan, filling each cavity about 2/3 full.
Bake for 10-12 minutes, or until the donuts spring back when lightly touched. Let them cool in the pan for a few minutes before transferring to a wire rack to cool completely.
For the frosting, mix the melted butter, powdered sugar, heavy whipping cream, vanilla extract, and cream cheese (if using) in a bowl until smooth and creamy.
Once the donuts are completely cooled, spread the frosting on each donut using a spatula.
Sprinkle some red velvet cake crumbs, decorative sprinkles, or drizzle melted white chocolate on top for an extra touch.
Serve with a glass of milk or a hot cup of coffee for the ultimate treat. Enjoy your homemade Red Velvet Donuts!