Ingredients
1 medium red onion, about 5 ounces
1/2 teaspoon sugar
1/2 teaspoon salt
3/4 cup rice vinegar, white wine vinegar, or apple cider vinegar

Flavorings (optional):
1 small clove of garlic, halved
5 black peppercorns
5 allspice berries
3 small springs of thyme
1 small dried chili

Instructions
Slice the onions: Start 2 or 3 cups of water on to boil in a kettle. Peel and thinly slice the onion into approximately 1/4-inch moons. Peel and cut the garlic clove in half.
Dissolve the sugar and salt: In the container you will be using to store the onions, add the sugar, salt, vinegar, and flavorings. Stir to dissolve.
Par-blanch the onions: Place the onions in the sieve and place the sieve in the sink. Slowly pour the boiling water over the onions and let them drain.
Add the onions to the jar: Add the onions to the jar and stir gently to evenly distribute the flavorings.
Store: The onions will be ready in about 30 minutes, but are better after a few hours. Store in the refrigerator. They will keep for several weeks, but are best in the first week.