Pickled Red Onion Rings

This recipe appeared in The Greens Cookbook, but because I find these beautiful pink onions so constantly useful as an ingredient and a garnish, I am including the recipe again. The onions lose their harshness and bite and are infused with pink within 15 minutes or so. They’ll keep for weeks, refrigerated. With their beautiful color and sweet-tart bite, they enliven everything they’re combined with—s