1/2 c. cider vinegar
1/4 c. water
2 tsp. dry mustard
1/2 tsp. salt
1/3 c. sugar
1/2 tsp. celery seed
2 c. sliced, cooked beets
1 medium onion, sliced

Heat vinegar and water to boiling; add mustard, salt, and sugar. Blend until mixed. Pour over combined celery seed, beets, and onions. Cover and place in refrigerator to marinate overnight or longer. Serve cold.