Pre-heat oven to 350 degrees F. Cover each skull in the pan with a thin layer of vegan butter.
Make a mixture of maple sugar and cinnamon and set it aside. (optional)
Place sifted paleo flour, maple sugar, yeast, salt, baking powder, and orange zest in a large mixing bowl.
In a separate bowl, mix butter, egg, orange juice, and milk. Pour the wet ingredients into the dry ingredients and mix with a hand mixer. Use a silicone spatula to scrape the sides.
Fill each skull with the batter about 3/4 of the way full. Place in the oven and bake for 15 - 20 minutes. Remove when the edges are golden or insert a toothpick to test.
Once you remove them from the oven, wait 5 minutes to flip the skulls into a cooling rack. Sprinkle with the sugar and cinnamon mixture while they are still hot.