Wash the beets and trim off the tops about 1/4 inch above the bulb.

Wrap each beet loosely in aluminum foil and place in the oven.

Roast until tender and easily pierced with the tip of a paring knife: about 1 hour.

Remove beets from oven and let cool in the aluminum packets.

When cool enough to handle, remove from the aluminum packets, discard the aluminum, and trim the leaf end flush to the bulb. Using your thumbs, push off the skin. Remove the beet skin under running water to minimize the stain on your fingers, or use gloves.

Cut the cooked beets into 1-inch chunks.

In a blender or food processor, combine the beets, walnuts, garlic, vinegar, za'atar, and salt. Blend to just combine.

With the motor running, slowly drizzle in the oil. If the mixture is too thick, add water 1 tablespoon at a time until the desired consistency is reached.

Chill for for 1 hour before serving.