Thinly slice the onions and place in a colander. Rinse with very hot water, then add to a 1-pint jar or container. Add sliced garlic.
Add vinegars, water, salt and pepper to a microwave-safe bowl and stir to combine. Microwave for 30 seconds. Pour over onions in jar. Refrigerate for at least an hour before eating.
Store in fridge for up to 2 weeks.
