Chopped Arabic Salad

Name: Chopped Arabic Salad
Ingredients: 1 lemon; 3/4 teaspoon salt; 1/4 teaspoon black pepper; 3 tablespoons olive oil; 2 (1/2-lb) cucumbers, peeled, halved lengthwise, seeded, and cut into 1/4-inch dice (2 1/3 cups); 1 lb tomatoes (3 medium), cut into 1/3-inch dice (2 1/2 cups); 1 cup finely chopped red onion (1 small) or 1 cup chopped scallions (about 5); 1 cup coarsely chopped purslane (optional); 1 cup finely chopped fresh flat-leaf parsley (from 1 large bunch); 1/2 cup finely chopped fresh mint (from 1 bunch)