Rustic tomato-bread salad

4 cups fresh tomatoes, diced into 1/2-inch pieces (1 1/2 pounds, about 5 medium tomatoes)
3/4 cup slivered red onion
1/2 cup water
1/3 cup olive oil
1/3 cup white-wine vinegar
1 teaspoon ground black pepper
1 teaspoon salt
1 teaspoon sugar
1/2 cup shredded fresh basil
6 cups day-old dense crusty bread, cut or torn into 1-inch cubes (about 1/2 pound)

Combine all ingredients except bread in large bowl; let stand for flavors to develop, about 10 minutes. Add bread; toss well to coat. If bread seems dry, sprinkle with an additional tablespoon or two of water. Salad will hold several hours at room temperature before serving.