Preheat oven to 375 degrees F (190 C), remove the stem and most of the root from your beets, and scrub and wash them underwater until clean.
Wrap beet(s) in foil, drizzle on a bit of olive or avocado oil, wrap tightly, and roast for one hour or until a knife inserted falls out without resistance. They should be tender. Set in the fridge (in a bowl to catch juice) to cool to room temperature.
Once cooled, either finely grate or purée beets in a small blender (adding orange juice or water to encourage mixing). Measure out 1/2 cup and set aside (amount as original recipe is written // adjust if altering batch size). Reserve the rest for things like beet hummus!
Line a muffin pan with paper liners.
Whisk together the almond milk and vinegar in a large bowl, and set aside for a few minutes to curdle. Add the sugar, oil, vanilla extract, and 1/2 cup beets (amount as original recipe is written // adjust if altering batch size) and beat until foamy.
Add the flour, cocoa powder, baking soda, baking powder, and salt to a sifter and slowly sift it into the wet ingredients while mixing with a hand-held or standing mixer. Beat until no large lumps remain.
Pour batter into liners, filling 3/4 of the way full. Bake 22 to 25 minutes (at 375 degrees F or 190 C), or until a toothpick inserted into the center comes out clean. Transfer to a cooling rack and let cool completely. Do not try and unwrap them or they'll stick to the wrapper.
Once cooled, dust with cocoa powder and store in an airtight container to keep fresh.