Place the sliced onions in a pint size mason jar or glass container.

In a saucepot bring the vinegar, lime juice, water, brown sugar, black pepper, kosher salt and coriander, if desired, to a boil over medium high heat.

Reduce to medium heat and simmer until the sugar is dissolved.

Pour the hot liquid over the onion slices.

Let cool to room temperature and then seal and refrigerate for at least one hour or until chilled.