Red Onion Storage
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Unless you're using iced water to purposely leach out the spiciness or the color from red onions, onions should not be stored in water overnight. Even when using the technique to as described above, it's done fairly quickly. A lot of times, I'll take paper thin shavings of red onion and put them in an ice bath for a short period to use for garnish or in salads. Otherwise, storing them in water is never a good idea.