Preheat oven to 400F. Wash and trim beets, then toss with olive oil and salt. Wrap in aluminum foil, or place in a lidded baking dish. Roast for about 45 minutes (will vary with beet size and age) until tender when poked with a fork or slim knife. Let cool, then rub off the peel with your hands. Use a knife to remove any areas of stubborn peel.

In a high speed blender, blend the beets with buttermilk and lemon juice until smooth. Adjust salt and pepper to taste. Refrigerate until chilled.