Preheat your oven to 350°F (175°C) and grease your donut pan with butter or non-stick spray.
In a large mixing bowl, combine the melted butter, sweetener, eggs, heavy cream, and vanilla extract. Whisk until smooth.
In another bowl, mix the almond flour, baking powder, and optional cinnamon. Stir until evenly distributed.
Gradually add the dry mixture to the wet ingredients, mixing until just combined.
Spoon the batter into the prepared donut pan, filling each cavity about ¾ full.
Bake for 15-20 minutes or until golden brown and a toothpick inserted comes out clean.
Let the donuts cool for about 5 minutes in the pan, then transfer to a cooling rack. Roll in granulated sweetener while warm.
