This salad is wonderfully refreshing even without purslane, but if you can find the green at your produce market, it's worth using for the nice crunch it adds.

　　Active time: 30 min Start to finish: 30 min

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)

　　Cut peel, including all white pith, from lemon with a sharp paring knife. Working over a bowl, cut segments from half of lemon free from membranes and transfer segments to a cutting board, then squeeze juice from membranes and remaining 1/2 lemon into bowl. Transfer 2 tablespoons juice to a large bowl, then finely chop segments and add to measured juice. Add salt, pepper, and oil, whisking to combine, then stir in remaining ingredients.