Place sliced onions in a baking dish, cover with buttermilk, and soak for at least an hour.
Combine dry ingredients and set aside.
Heat oil to 375°F in a Dutch oven. Grab a handful of onions, throw into the flour mixture, tap to shake off excess, and plunge into hot oil. Fry for a few minutes and remove as soon as golden brown. Season with salt and pepper as desired and serve immediately.
Repeat with remaining onions.
Notes
Source: Adapted from the Pioneer WomanYou're Gonna Bake It After Allbakeitafterall.com