Slice your cucumbers and red onion really thin. Thin slices soak up vinegar real good and stay tender but with a crisp bite.
Toss those fresh veggies into a big bowl that can hold everything nice and comfy.
In another bowl, mix the apple cider vinegar, sugar, water, and salt. Whisk till the sugar is all gone. No grainy bits left over 'cause that’s just messy.
Pour that tangy vinegar mix all over your cucumbers and onions. Toss it well so every slice is coated with the tang and sweetness.
Now for the pressure cooker part. You don’t gotta cook cucumbers long but getting a little warm in sealed steam helps flavors meld.
Notes
Serve chilled for maximum freshness and flavor. For a little spice, add chili flakes or pepper to taste.