This recipe is a winner because it's so simple and flexible. You can use this same brine to quick-pickle sliced japaleños or radishes. Or even do a combo of all three.
Cut the onion in half, and then thinly slice it either into half-moons or vertically. Place it in a medium heatproof bowl or a 2- to 3-cup heatproof glass jar.
Combine the vinegar and remaining ingredients in a small saucepan. Bring to a boil, swirling the pan occasionally. Cook just until the sugar and salt dissolve. Pour over the onions. Cool to room temperature. Cover and refrigerate up to 2 weeks.
Notes
Adapted from Trejo’s Tacos by Danny Trejo and Larchmont Hospitality Group LLC (Clarkson Potter)