1. Peel the red onions, trim the ends, and cut them into chunky wedges or thick slices. Pack the onions into a heat-safe jar or shallow dish.

2. In a small saucepan, combine the apple cider vinegar, water, honey, kosher salt, smashed garlic cloves, black peppercorns, and crushed red pepper flakes. Stir to begin dissolving the honey.

3. Set the saucepan over medium heat and bring the mixture just to a gentle simmer, stirring occasionally, until the honey and salt are fully dissolved.

4. Carefully pour the hot brine over the onions, making sure they are mostly submerged, and use a spoon to press any stray pieces down into the liquid. Let the onions stand at room temperature for 20–30 minutes.

5. Drizzle the extra-virgin olive oil over the onions and sprinkle with the chopped parsley or cilantro, then gently stir so every piece is coated in the hot honey brine.

6. Cover the jar or dish and refrigerate for at least 1 hour, or until chilled and bright pink. For the best flavor, let the onions rest for 4 hours or overnight before serving.