Simmer 20-30 minutes:

2 c. apple cider vinegar
2 c. sugar
2 c. water
1 tsp. salt
1 tsp. ground cloves
1 tsp. allspice
1 tsp. cinnamon
1 tsp. celery seed
1 tsp. dry mustard

Pour over thin sliced green tomatoes and Bermuda onions in a large glass bowl. Cover and refrigerate for at least 8 hours. To serve - spoon into a relish dish.