Place the sliced onion in a small bowl of cool water, and soak for 10 minutes to reduce its astringency, then drain and pat dry with paper towels. Place the cucumbers and tomatoes in a colander suspended over a bowl, then toss with 1 tbsp of the kosher salt; set aside for 10 minutes, stirring to drain any accumulated water; gently pat dry to remove excess moisture.

In a large mixing bowl, combine the onions, tomatoes, cucumbers, chives, dill, and parsley. In a small bowl, combine the lime juice, olive oil, and black pepper. Pour the lime dressing into the mixing bowl and toss to combine; season with salt and pepper to taste, then serve.