Classic Italian Panzanella Salad

2 medium tomatoes, cut into 1-inch cubes (or 2 cups cherry tomatoes, halved) 1/2 tsp fine sea salt 2 cups good quality Italian bread, such as multigrain Ciabatta 1 cup cucumber, quartered lengthwise and thinly sliced (about 1/2 an English cucumber) 2 stalks celery, sliced 1/2-inch thick 1 small red onion, cut in half and thinly sliced 1/4 tsp freshly ground black pepper 2 Tbsp red wine vinegar 2 Tbsp extra virgin olive oil 1/2 cup fresh basil leaves, torn into strips 1 cup flat Italian parsley leaves, roughly chopped