Making Pickled Red Onions is a quick, simple process. Follow these steps closely for the best texture and flavor.

Step 1: Prep the Onions

Peel the red onions and slice them into thin rings or half-moons, depending on your preference. A mandoline can help achieve thin, even slices quickly and consistently, which is important for even pickling.

Step 2: Pack the Jars

Place the sliced onions into a large, clean glass jar, or divide them between two quart-sized jars.

Step 3: Add the Aromatics and Spices

Add the sliced garlic, bay leaves, black peppercorns, mustard seeds, coriander seeds, fresh dill if using, and crushed red pepper flakes evenly throughout the jars, distributing everything so the flavor infuses consistently.

Step 4: Build the Brine

In a medium saucepan, combine the white vinegar, water, pickling salt, and sugar.

Step 5: Heat Gently

Heat over medium heat, stirring until the salt and sugar are completely dissolved. Do not let the brine boil.

Step 6: Pour Over the Onions

Carefully pour the warm brine over the onions, making sure they are completely submerged.

Step 7: Cool and Seal

Seal the jars tightly and allow them to cool to room temperature.

Step 8: Refrigerate and Wait

Refrigerate for at least 24 hours before serving. For the richest flavor, allow the onions to pickle for 3 to 5 days, giving the brine time to fully penetrate each slice.