Step 1 of 4

Soak the rings in buttermilk

Separate the onion slices into rings, put them in a bowl with the buttermilk and a teaspoon of the salt, and leave them for at least 30 minutes.

— The soak does two jobs: it takes the raw bite out of the onion, and it leaves a film that the flour clings to instead of falling off in the oil.