1. Slice the cucumbers into 1/4-inch (1/2 centimeter) thick slices. Toss with kosher salt and place in a colander set in a bowl. Place a large ziplock bag filled with water on top of the cucumbers to weigh them down and force out the liquid. Leave them this way for one to three hours. Transfer cucumbers to a medium bowl and set aside. (This can be done the night before — just be sure to store the cucumbers in a container with a strainer at the bottom to maintain their crispness.)
2. Meanwhile, roast the peppers: Preheat oven to broil. Slice the tops and bottoms off the peppers, and core. Lay them flat open, skin-side up, on a pan lined with Gefen Parchment Paper or foil. Roast until the skin is charred and puffed, but the flesh is still firm.
3. Remove the pan from the oven and let the peppers sit until cool enough to handle, but still very warm. The hotter they are, the easier they are to peel. Start peeling where the skin is most charred. Once peeled, cut into strips or small pieces.
4. To make the dressing, whisk the vinegar, black pepper, and oil together in a small bowl. Add the onion. (This can also be done the night before.)
5. To assemble: Place cucumbers, roasted pepper pieces, and mint leaves in a bowl. Add dressing and toss to combine. Taste and adjust seasoning if necessary, adding more salt and/or pepper. Garnish with mint leaves. Serve immediately.
I like to prepare all the components of this salad in advance, and then toss it together right before serving. I always underestimate how much I’ll need because it doesn’t keep well after it’s dressed.