Using a sharp knife, carefully slice your cucumber into 1/8-inch-thick slices.
Thinly slice the red onion.
In a medium glass bowl, whisk together the vinegar, water, maple syrup or honey, sea salt and red pepper flakes.
Place the sliced cucumber and onions into a clean 17oz. wide mouth glass jar.
Pour in your vinegar mixture, and make sure the veggies are completely submerged.
Seal with it's lid, then refrigerate for at least 2 hours before serving.
Serve and enjoy!
Your pickled cucumber salad will keep well refrigerated for up to 5 days and it will actually taste better after a couple of days