Toast the Sourdough Bread. Preheat your oven to 400°F and line a rimmed baking sheet with parchment paper.
Cut your stale sourdough bread into 1-inch cubes and spread them in an even layer on the baking sheet. Drizzle with olive oil and toss until lightly coated.
Bake for 10-15 minutes, or until the bread is lightly golden and crisp around the edges. Set aside to cool slightly.
While the bread is toasting, wash and chop your vegetables.
Add the fresh tomatoes, English cucumber, red onion, fresh basil, and any additional vegetables you're using to a large mixing bowl. If using larger heirloom tomatoes, cut them into bite-sized pieces. If using cherry tomatoes or grape tomatoes, simply slice them in half.
In a small bowl, whisk together the extra-virgin olive oil, red wine vinegar, Dijon mustard, fresh garlic, kosher salt, black pepper, and fresh lemon juice until well combined.
The dressing should be bright, flavorful, and slightly tangy—the perfect complement to the sweet tomatoes and sourdough bread.
Add the toasted sourdough cubes to the large bowl with the vegetables. Pour the dressing over the salad and gently toss until everything is evenly coated.
If you're using fresh mozzarella, add it now and gently fold it into the salad.
Let the Salad Rest. This step is important for the best results. Allow the salad to rest at room temperature for about 15-20 minutes before serving.
As the salad rests, the sourdough croutons will absorb the tomato juice and dressing, creating the signature texture that makes a classic Tuscan bread salad so delicious.
Transfer the salad to a large platter and finish with an extra drizzle of olive oil, additional fresh basil, and a sprinkle of flaky salt if desired.
Serve immediately alongside grilled meats, sandwiches, or your favorite summer meals. This rustic tomato salad is especially delicious at cookouts, potlucks, and summer picnics.
