Thinly slice the cucumbers on a mandoline between 1/8” – ¼” thick. Place in a large bowl and gently toss with 2 tablespoons of salt. Place the bowl in the refrigerator for 30 minutes to rest.

While the cucumbers rest, combine the cider vinegar, red wine vinegar, water, and sugar in a saucepan. Place over medium heat, whisking until the sugar has dissolved; do not boil. Once sugar has dissolved, remove from heat and add the red onion. Allow the onion to marinate in the brine for about 20 minutes.

After the cucumbers have rested, drain off any liquid that has sweat out from them and quickly rinse in cold water and drain well.

Toss the cucumbers and pickled onions in a large bowl with about half of the brine. Add the fresh herbs. Toss to combine, then taste for seasoning, adding additional salt and pepper or more of the brine as desired. 

Serve immediately or chill in the fridge for 1-2 hours before serving.