Place onions, oregano, salt and lime juice into a medium bowl.
Mix together vinegar and water and pour it into the bowl.
Mix everything for one minute and adjust with salt and oregano if needed.
Let it marinate for 10 minutes and serve.
These Mexican pickled onions can be eaten straight away after being prepared, but if you want to enjoy their flavor 100% and bring out that marvelous bright color, I recommend that you let them marinate for at least a whole day. You will see that the taste becomes even more delicious.
If you’re lucky enough to get Mexican oregano, use that one, because it definitely tastes different (and more delicious, in my opinion) and is perfect for this recipe.
You can prepare this recipe with any type of onions such as white, golden, red (purple), or even spring onions.