Instructions

1. Heat the vinegar mixture

   In a small saucepan, stir together the vinegar, water, salt and your desired amount of sweetener. Cook over medium-high heat until the mixture reaches a simmer. (Or alternately, you can heat the mixture in the microwave.)

2. Combine in a jar

   Place the thinly-sliced onions in a mason jar. Pour the hot vinegar mixture over the onions, screw on the lid, and shake the onions briefly until they are evenly coated with the vinegar mixture.

3. Marinate

   Press the onions down with a spoon to get the top ones wet, then close the jars to marinate for 30 minutes.

4. Serve

   Serve immediately, or refrigerate the onions in a sealed container for up to 2 weeks.