Ingredients :

• The onions — Take yellow onions, not red ones. Yellow ones have firmer flesh that holds up better to frying and a slightly sweet taste that balances the salty batter. Cut the rings thick—at least one centimeter. Too thin, and they disappear into the batter.
• Buttermilk — This is what really makes the difference. Its acidity slightly tenderizes the onion and, above all, it makes the batter stick like nothing else. If you can’t find any, mix 1 cup of milk with 1 tablespoon of lemon juice, wait 5 minutes—it works very well.
• Cornstarch — Half flour, half cornstarch: that’s the secret to the crunch. Cornstarch absorbs less oil and forms a lighter crust than flour alone. Don’t replace it with potato starch; the result really isn’t the same.
• Paprika — Use sweet paprika rather than smoked for this recipe. It gives the batter that appetizing brick-orange color and a slightly sweet-spicy background that enhances everything without taking over.