0 Thinly slice your large red onion and put it in a jar.
1 Mix the vinegar, hot water, sugar, and salt until dissolved, then pour over the onions.
4 Cool it completely, lid on, and place it in the fridge.
2 Let it sit for at least 60 minutes (overnight for the best flavor).
3 Keep for 2-3 weeks in the fridge. Enjoy on bagels, wraps, salads, or any way you like!
