– 2 tablespoons red-wine vinegar
– 1 teaspoon Dijon mustard
– 1 teaspoon salt
– 1/2 teaspoon sugar
– 1/2 teaspoon black pepper
– 1/2 cup extra-virgin olive oil
– 4 lb mixed heirloom tomatoes, quartered if small or cut into 1/4-inch-wide wedges if larger
– 1 lb cherry tomatoes
– 1 lb very small mozzarella balls (1/4 inch; sometimes called perlini) or 1 lb lightly salted mozzarella, cut into 1/4-inch pieces
– 1 1/2 cups loosely packed small basil leaves or torn large leaves


Whisk together vinegar, mustard, salt, sugar, and pepper in a large bowl.
Add oil in a slow stream, whisking constantly until dressing is emulsified.
Add tomatoes, mozzarella, and basil and toss well.
Season with salt and pepper.

– Salad, without vinaigrette, can be assembled 2 hours ahead and kept at room temperature. Salad can be dressed 1 hour ahead and kept at room temperature, covered.
– Vinaigrette keeps, covered and chilled, 1 week.