- Thinly slice the red onion using a mandolin or sharp knife.
- Wash and dry the glass jar with tight fitting lid.
- Place thinly sliced red onion into glass jar.
- In a small pot, combine water and vinegar, sugar and salt and bring to a simmer for 5 minutes.
- Remove from heat and add fennel seeds and peppercorns.
- Pour warm mixture into glass jar over the onions and cover onions with liquid.
- Let sit for 30minutes.
- Enjoy or place in the fridge. Can be eaten for up to 2 weeks.