- 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.