Hawaiian salt, sugar, vinegar, water, and a saucepan over high heat. Heat through after bringing to a boil until the sugar and salt have dissolved. Place this aside to gently cool.
Place onions in a jar or other container after thinly slicing them.
Over the onions, cover them completely with the pickling juice. At room temperature, let cool.
Put the lid on and keep the container in the fridge. ENJOY!