Remove stem from the beet, wash it thoroughly and lightly coat with high heat oil then wrap in tin foil. Place on a baking sheet and cook in the oven at 425°F for 45 minutes to an hour, or until soft. You can use an oven mitt to squeeze it and see if it is pliable, it indicate it is done. Remove from the oven and set aside to cool for at least an hour. Peel the skin off cut off any hard spots, and dice the roasted beet and measure out 1/2 cup for the recipe.
Preheat the oven to 350°F then grease or line a muffin pan for 10 cupcakes.
In a large bowl, sift together the dry ingredients (oat flour to baking soda), making sure to work out any large lumps, then set aside.
Stir together the almond milk and the apple cider vinegar in a measuring cup and allow to sit for a few minutes to curdle. Add it to a blender or a food processor along with the 1/2 cup diced and roasted beet, coconut sugar, pure maple syrup and vanilla extract. Blend on high for about 20 seconds, or until a smooth liquid forms.
Pour the liquid into the bowl with the dry ingredients then add the melted coconut oil last. Use a spatula to fold everything together until well combined, making sure there are no lumps.
Using a scooper or a small dry measuring cup, fill each one about 1/2 full to make 10 cupcakes. Bake in the preheated oven for 20 minutes, or until you can stick a knife in the centre and have it come out clean.
Meanwhile, prepare the frosting by combining all of the ingredients in a blender or a food processor and blending until smooth. Scrape down the sides a few times in between blending. Taste test, and add more maple syrup to make it sweeter.
Allow the cupcakes to cool completely before frosting them. Use a knife to spread the frosting on top or transfer it to a bag for piping. Store leftovers in an airtight container in the refrigerator for up to 2 days.