Leave the root and 1 inch of stem on beets, and scrub with a brush. Steam beets and bay leaf, covered, for 30 minutes or until tender. Discard bay leaf. Drain and rinse beets with cold water. Drain. Trim off beet roots; rub off skins. Cut beets into 1/4-inch slices. Combine beets and onion; arrange on a platter.
Combine parsley and next 4 ingredients (parsley through salt), stirring with a whisk. Pour dressing over beet mixture. Sprinkle with pepper, if desired.