These easy refrigerator pickled red onions have a bright, tangy flavor and make a delicious topping for all types of sandwiches, burgers, tacos and salads.
Trim the ends from the onion, halve lengthwise, remove the skin, and slice thinly (about 1/8-inch). Separate the slices and set aside.
Add the rice vinegar, red wine vinegar, sugar, garlic, peppercorns, and salt to a small saucepan. Bring to a simmer over medium-high heat, and stir until the sugar dissolves.
Add the onions, stir until they're submerged in the liquid, and continue cooking just long enough for them to soften (1 to 2 minutes). Remove the pan from the heat and let stand until cooled, stirring occasionally.
Once the onions have cooled, transfer the onions to a glass jar with a tight-fitting lid, pour the pickling liquid over them, and refrigerate until thoroughly chilled before serving.
Refrigerated and stored in their pickling liquid, onions will keep for up to 2 weeks.
Notes
About the vinegar: We use a combination of rice and red wine vinegar for our pickled red onion recipe - rice vinegar for its mild flavor and lower acidity, and red wine vinegar to enhance color. This combination is flexible though. You could use apple cider vinegar, white wine vinegar, or distilled white vinegar in place of the rice vinegar depending on what you have on hand. They all have a higher acidity level however so you may want to replace a little of the vinegar (2 to 3 tablespoons) with water.