2 1/2 pounds (1.1kg) mixed ripe tomatoes, cut into bite-size pieces
2 teaspoons (8g) Diamond Crystal kosher salt, plus more for seasoning (use half as much if using table salt)
3/4 pound (340g) ciabatta or rustic sourdough bread, cut into 1 1/2–inch cubes (about 6 cups bread cubes)
10 tablespoons (150ml) extra-virgin olive oil, divided
1 small shallot, minced (about 2 tablespoons)
2 medium cloves garlic, minced (about 2 teaspoons)
1/2 teaspoon Dijon mustard
2 tablespoons white wine vinegar or red wine vinegar
Freshly ground black pepper
1/2 cup (1/2 ounce) packed basil leaves, roughly chopped
Place chopped tomatoes in a colander set over a bowl and season with 2 teaspoons (8g) kosher salt. Toss to coat. Set aside at room temperature to drain, tossing occasionally. Drain for a minimum of 15 minutes.
Meanwhile, preheat oven to 350°F (180°C) and adjust rack to center position. In a large bowl, toss bread cubes with 2 tablespoons (30ml) olive oil. Transfer to a rimmed baking sheet. Bake about 15 minutes, until crisp and firm but not browned. Remove from oven and let cool.
Remove colander with tomatoes from bowl with tomato juice. Place colander with tomatoes in sink. Add shallot, garlic, mustard, and vinegar to bowl with tomato juice. Whisking constantly, drizzle in remaining 1/2 cup (120ml) olive oil. Season dressing to taste with salt and pepper.
Combine toasted bread, tomatoes, and dressing in a large bowl. Add basil leaves. Toss everything to coat and season with salt and pepper. Let rest 30 minutes before serving, tossing occasionally until the dressing is absorbed by the bread. Notes Use a hearty, open-structured bread, like ciabatta or sourdough.