Combine all ingredients in a heavy kettle (a enamel-lined dutch oven works really well here. Don’t use a straight cast iron one here, all that vinegar will strip away your seasoning). Bring to a boil and simmer gently until slightly thickened (the recipe calls for 45 minutes of cooking time, I’d cut it a bit shorter if you want your rhubarb to maintain some of its texture/identity). Stir frequently, otherwise it will stick (and sticking leads to scortching, so stir, stir, stir).

When the texture pleases you, pour into clean pint jars and process in a hot water bath for ten minutes.