1. Bring rhubarb and vinegar to a simmer in a medium nonreactive saucepan over medium heat and cook for 2 minutes; remove from heat. Stir and press mixture against sides of pan to release juices and let cool slightly.
2. Pour warm vinegar mixture into a large, clean jar. Cover and store in a cool, dark place for 5 days.
3. Line a fine-mesh strainer with a coffee filter or cheesecloth and set over a large measuring cup or bowl. Strain vinegar and transfer to a clean bottle.
Source: Hannaford fresh Magazine, May - June 2016