Preheat your oven to 400F. Rub the beet with a light coating of olive oil. Wrap the beet tightly in foil or parchment. Roast it for 45 minutes-1 hour, or until it's completely tender when pierced with a knife. When the beet has cooled for about fifteen minutes, run it under cold water while you slip off the skin. Cut the beet into quarters.
Blend the beet and all remaining ingredients in a blender or a food processor till they’re completely smooth. Adjust the salt as needed. If the dressing is a bit thick, add in water by the teaspoon.
Serve the dressing over salads, bowls, or on a sandwich. The dressing will keep for up to 5 days in an airtight container in the fridge.