Pick over the pomegranate seeds, removing any white pith and/or any bad seeds and place them in a saucepan.

Crush the fruit lightly to release its juices. A flat-bottomed metal dry measuring cup, works really well.

Pour in the vinegar and bring everything to a simmer (small bubbles only, you don't want to bring it to a boil) for just one minute to help infuse the vinegar, and turn off the heat immediately.

Pour everything — vinegar and fruit — into a hot sterilized jar (it's easier to work with jars with a wide opening). Cover the jar loosely with a kitchen or paper towel and let it cool completely.

Cap the jar and put it in a dark cupboard, or in the fridge. The flavor keeps developing as the days go by and the seeds steep, but you can use it as soon as you need it.

If you want, strain the fruit before using. You could add a bit of sweetener like honey or even a drizzle,of pomegranate molasses to enhance the flavor even more.

NOTE on how to sterilize a mason jar:

Wash the jars, lids and bands with soapy water. Rinse well. Put the jars (not the bands or lids) right side up on a rack in a large pot or saucepan of hot water (not boiling yet). There should be enough water to reach 1 inch above the tops of the jars. Boil 10 minutes and then lower the heat to a simmer until ready to use. Remove jars with tongs just before using, shaking off excess water and transferring onto a clean kitchen towel.