Salad-e Shirazi (Persian Cucumber, Tomato and Onion Salad)

to 4 Persian cucumbers (about 3/4 pound)

red onion, diced into 1/4-inch pieces

any combination of finely chopped fresh parsley, cilantro, basil or dill

dried mint

to 3 medium tomatoes (about 1 pound)

freshly squeezed lime juice (from about 2 limes), plus more as needed

extra-virgin olive oil

Fine sea salt and freshly ground black pepper