You can use these onions for "just about anything—in sandwiches, with grilled meats, in grain bowls, you name it," says chef Josef Centeno from BäcoShop.
Place the onion in a large heatproof bowl. In a small saucepan, bring the vinegar, oil, chile, sugar and 1/2 tsp. salt to a boil over high heat, stirring until the sugar and salt dissolve. Pour over the onions. Stir in the mint, basil and 3 grinds of black pepper. The pickled onions can be used right away, or transfer them to a pint-size jar with a lid, cover and refrigerate up to 1 week.