Preheat the oven to 180°C. Line a small square baking tin with baking paper.
Place the avocado and cooked beetroot in a food processor and blend until smooth.
Add the cocoa powder, maple syrup and almond butter and blend again until thoroughly combined.
Add the flour and baking powder and mix until you have a thick, smooth batter. If the mixture seems unusually thick, add a tablespoon of water at a time until it reaches a spreadable consistency.
Transfer the mixture to the prepared tin and smooth the top.
Bake for 20–25 minutes, until the top is set but the centre remains slightly soft.
Allow to cool completely in the tin before cutting into squares. The brownies will firm up as they cool.