In a medium saucepan, bring the vinegar, water, sugar, peppercorns, coriander seed and cinnamon stick to a boil.
Turn the heat to low and stir in the onion. Simmer for 5 minutes.
Divide the beets among 8 ounce canning jars filling until about 1 inch from the top of the jar. Do not pack the beets in tightly.
Pour the pickling brine and onions into the jars covering the beets. Allow the mixture to cool to room temperature, approximately 20 to 30 minutes.
Seal the jars with the lids and store in the refrigerator for up to 5 days.
How to Roast Beets: Arrange them on a baking sheet, and coat with olive oil. Roast them in the oven at 425 degrees for 30 to 40 minutes, or until fork tender. Allow to rest until cool enough to handle and then peel the skin off with your fingers or a vegetable peeler.