1. Preheat the oven to 325 degrees F. Arrange the bread cubes on a rimmed baking sheet in a single layer. Bake until dried out but not toasted, 10 to 15 minutes. Cool.
2. Meanwhile, put the tomatoes in a colander and toss them with 1 teaspoon salt. Let stand 20 minutes, discard any juices that drain out.
3. Whisk the olive oil and vinegar together in a large bowl. Add the bread, tomatoes, onion, and basil and toss to coat thoroughly. Season with salt and pepper and serve immediately.
Ingredients
5 cups cubed good-quality crusty bread (about half of a 7-inch round loaf) 6 medium-ripe tomatoes, cored and cut into 3/4-inch pieces Kosher salt and freshly ground black pepper 6 tablespoon extra-virgin olive oil 3 tablespoons sherry vinegar 1/4 cup thinly sliced red onion 1 cup basil leaves, torn