I often order a version of this when I am dining in Vietnam, and I almost always make it for my table at home. The key is good cucumbers and tomatoes—don’t even attempt to use the pinkish winter tomatoes and the standard waxed cucumbers from most supermarkets, or you will be disappointed. The dressing is designed to bring out the flavors in fresh foods and not to hide them. I also find myself dipping a tomato or cucumber slice from this salad into the dipping sauce on the table for an extra burst of salty flavor. The vegetable oil is a Western option but does add a nice flavor balance and gives the salad some shine. I sometimes add freshly ground black pepper just before serving. 1 Peel the cucumbers, or not, as you wish, then thinly slice and arrange on a plate with the tomatoes. 2 Mix the vinegar, lime juice, garlic, sugar, salt, shallots, and chile in a bowl, and let sit for a few minutes to allow the flavors to mingle. Whisk in the oil, if using, and pour over the tomatoes and cucumbers.
