Remove the skin from the Roasted Beets and slice thinly. Arrange in 1-quart jars alternating layers with the onion. In a small pot boil the rest of the ingredients and pour over the beets. Tightly lid the jars and place in the refrigerator for 3 to 7 days before serving.
Preheat oven to 400 degrees F.
In a large bowl toss all of the ingredients. Place into a foil pouch and roast in the oven for 40 minutes.
Recipe courtesy of Alton Brown