Prepare the Onions – Use a sharp knife to trim ½-inch from the stem end and ¼-inch off the root end. Cut in half lengthwise with the stem-side down, then peel. Slice each half into ⅛ to ¼-inch thick pieces. Alternatively, cut into rings.
Heat the Pickling Liquid - In a small saucepan, add distilled white vinegar, apple cider vinegar, honey, and salt. Bring to a boil over medium-high heat, stirring to dissolve the honey and salt—Cook for about 2 minutes.
Pickle the Onions - In a medium bowl or glass jar, add the sliced onions. Pour the pickling liquid on top, pressing down to submerge.
Cool - Let the pickled onions sit at room temperature for 30 minutes to cool completely. Check every 10 minutes, submerging the onions with a spoon if needed.
To Serve - Use immediately or cover and store in an airtight container for up to 2 weeks.
Recipe Yield: About 1 cup
Serving Size: About 2 tablespoons
Onion Substitutions: Use white, yellow, or sweet onions, shallots instead of red onions.
Substituting Honey: Use ¼ cup maple syrup (to make it paleo) or ⅓ cup granulated sugar.
Optional Flavorings: Dried bay leaf, a sprig of thyme, whole peppercorns (5), sliced garlic clove, red pepper flakes (⅛ to ¼ teaspoon), dried red chili, whole clove, cinnamon stick, pickling spice (½ to 1 teaspoon), allspice berries (3 to 5).
Storing: Store onions in the pickling liquid in an airtight container like a mason jar. Refrigerate for 1 to 2 weeks.