How to Make It
Stir together onion, chile slices, and salt in a medium bowl. Let stand at room temperature, stirring occasionally, until onions are slightly softened, about 5 minutes.
2. Stir in lime juice, and let stand, stirring occasionally, until onions are pickled, about 30 minutes. Drain onion mixture. Cover and refrigerate until ready to use, up to 1 day.