Starting thinly, thinly (did I say thin?) cutting your onion into rings. Remember, these are onion strings, not onion rings, so they need to be super thin. Make sure you are using a sharp knife or a mandolin slicer. Separate onion rings and place into a shallow dish.
Cover onions with buttermilk, tossing until all covered. Set aside at room temperture, tossing every 10-15 minutes to ensure they are all marinating evenly.
In a medium mixing bowl, combine flour, salt, ground black pepper and celery salt.
Fill a large, heavy bottom pan with 2 inches of vegetable oil. Heat to 375 degrees.
Working in batches, use a slotted spoon or your fingers to remove onions from buttermilk, tapping to remove any excess liquid. Drop into flour mixture, turn to coat and then carefully place in hot oil.
Fry for 3-4 minutes, or until lightly brown. Remove to a paper towel lined baking sheet or plate to drain.
Continue with remaining onions.
If you've tried this recipe, come back and let us know how it was!