Preheat oven to 400. Wrap the beets up in aluminum foil and place on a baking sheet. Bake for 1 hour or until tender. Remove from the oven and let them cool. When they are cool enough to handle, peel them and cut them into quarters.
Add the beets, salt, lemon juice, and tahini into a food processor. Process until smooth (you might need to pause to scrape down the sides.) Add the olive oil and process again until combined.
Store in an airtight container in the fridge for up to 5 days, or freeze.