Slice the onion crosswise into 1/4-inch thick slices to yield about 2 cups of onion rings.

Place onion rings in a heat-proof bowl.

Pour boiling water over the onion rings, ensuring they are submerged.

Let the onions sit in the boiling water for 15 seconds.

Immediately drain the boiling water from the onions.

Rinse the onions with cold water to stop the cooking process.

Drain the onions thoroughly.

In a separate bowl, combine olive oil, cider vinegar, and hot pepper sauce.

Whisk the mixture together with a fork until well combined.

Pour the dressing over the drained onion rings.

Toss the onions to ensure they are evenly coated with the dressing.

Let the pickled onions sit at room temperature for at least 30 minutes to allow the flavors to meld.

Serve and enjoy; do not refrigerate.