Chop the red onion to your desired size. I like to cut it lengthwise for this dish.
Mix all of the ingredients with the onions in a large bowl. Best if mixed by hand so you can ensure a thorough mix has been done. Feel free to wear a glove :).
Serve immediately or refrigerate until ready to serve. Feel free to marinate for up to 3 days if you prefer softer marinated onions.