For onion rings, I like to soak my onions in buttermilk because it tones down the sharp flavor of the onion and the buttermilk adds a lot of flavor. If you don't have buttermilk on hand, you can make your own by combining 1 cup of milk with 1 tablespoon of lemon juice, then let the mixture sit for 10 minutes. Another option is to soak your onions in ice water.