¼ cup Apple cider vinegar
¼ cup White balsamic vinegar
½ cup Water
1½ tsp Kosher salt
1 large or 2 small Red onions, thinly sliced
Outdoor grill or Grill pan
In a small saucepan, bring the apple cider vinegar, balsamic vinegar, ½ cup of water, and salt to a boil. Boil until the salt dissolves, about 1-2 minutes. Remove from the heat and let cool a minute or two.
Add the sliced red onions to a glass jar and pour the vinegar over the onions. Let the onions sit at least 30 minutes at room temperature before using or place in the fridge for up to 2 weeks.