Slice the onions into ½-inch thick rings and separate the rings.
In a large bowl, mix flour, baking powder, salt, and pepper.
Pour buttermilk into another bowl.
Dip each onion ring into the flour mixture, coating well.
Then, dip the floured onion rings into the buttermilk.
Coat the rings in breadcrumbs for extra crunch.
Heat oil in a deep pan to 350°F (175°C).
Carefully place the coated onion rings in the hot oil, frying a few at a time.
Fry for about 2-3 minutes or until golden brown.
Remove with a slotted spoon and drain on paper towels.