Slice the onions super thin. Like 1/8" thick. I use my mandolin so that they are all the same thickness.
If you are using jalapeños, slice them thin and put on top of the onions in your bowl before adding the rest.
2 Whisk the vinegar, sugar and salt together in a mixing bowl until the sugar and salt have dissolved.
3 Add the oregano and onions, cover and allow to rest for 2 hours.
4 Store in a jar or resealable glass container in the refrigerator for up to a month.
