Slice the onion: Thinly slice the red onion and place it in a clean jar or container. I like to carefully use a mandolin!

Mix the brine: In a measuring cup or bowl, whisk together the apple cider vinegar, salt, and honey until the salt and honey are fully dissolved.

Combine: Pour the vinegar mixture over the onions, pressing them down so they’re fully submerged. Add more vinegar if needed to cover. Press the onions down with a fork.

Let it sit: Let the onions sit in the fridge for at least 5 minutes to pickle. If you have time, leave them for 30–60 minutes before serving! Stir once or twice during that time to ensure even flavor.

Refrigerate: Once pickled to your liking, cover and refrigerate. Can be stored in the fridge for 3–4 days!