Slice the onion in half lengthwise from root to stem. Remove the outer layer or two of the onion then lay each half of the onion flat on the cutting board. Cut the root and stem off each side and thinly slice the onion into strips. Use your hands to separate the layers of strips.

Add the lime juice, red wine vinegar, salt, and sugar to a medium to large jar or bowl with a lid and stir it quickly to combine. Add the sliced onions and stir or close the lid and gently shake to combine. The pickling liquid will just cover the onions.

Close the lid and pickle the onion for at least 20 minutes. If you’re using these in a recipe like tacos, make the Mexican pickled onions first and let them marinate while you make the recipe and these onions will be ready. Store leftover onions in an airtight container in the fridge for up to 3 weeks.