Peel and half sweet onions.

Thinly slice.

Add to a disposable storage bag.

Pour in buttermilk and make sure the onion slices are well coated. This will help the flour adhere to the onion slices better.

Stir together flour and Cajun seasoning. Creole seasoning can be substituted for Cajun seasoning. I find store bought Creole seasoning to have a little less heat than my homemade Cajun seasoning. Try Tony Chachere's or Zatarain's  . For my homemade seasoning, I recommend two teaspoons. For the store bought versions I recommended, use a tablespoon.

Add to bag of onions and toss well to coat all the onions. Pour the onions coated with seasoned flour onto a tray. Sprinkle with additional flour as needed to ensure the onions are well coated.

In a pot or kettle that has deep sides, heat about 2 to 3 inches of cooking oil to 350 degrees.  Ensure that you have a deep pot because the hot oil will bubble up quite a bit due to the high water content of the onions. Using a shallow pot might result in a spillover of hot oil.  Be careful!

Working in batches, drop the breaded onions into the preheated oil. Stir continuously to help the onion pieces break apart. Once they start browning, they'll go quickly.  Don't get distracted or walk away. They only need about 4 minutes to brown.

As soon as they are to the shade of golden brown you like, remove them with a slotted spoon to a paper towel lined tray. Spread in an even a layer so they'll drain better.

Repeat with each batch.  Taste for seasoning and, if needed, sprinkle with additional seasoning while hot.

Transfer to a platter for serving. Or not.  Not a thing wrong with eating off the paper towel lined platter.