- 1 medium red onion, halved and thinly sliced
- 3 tablespoons fresh lime juice, plus the finely grated zest of 1 lime
- 3 tablespoons olive oil
- kosher salt
- 4 large tomatoes (about 2 1⁄2 pounds), sliced
- In a medium bowl, toss the onion with the lime juice, oil, and ½ teaspoon salt. Let stand, tossing occasionally, until the onion has softened, at least 1 hour and up to 3 hours.
- Arrange the tomatoes on a platter and season with ½ teaspoon salt. Top with the onion and sprinkle with the lime zest.