Italian Steak Salad with Parmesan Croutons

Name: Italian Steak Salad with Parmesan Croutons
Ingredients: 2 cups grape tomatoes (1/2 cup whole, 1 1/2 cups halved); 1/2 small red onion (1/2 cut into chunks, 1/2 thinly sliced); 1/4 cup fresh basil; 3 tablespoons red wine vinegar; Kosher salt and freshly ground pepper; 6 tablespoons extra-virgin olive oil; 1 1/4 pounds flank steak, halved lengthwise; 3 cups torn Italian bread (about 4 ounces); 2 tablespoons grated parmesan cheese, plus shaved parmesan for topping; 3 heads endive, cut into 1/2-inch pieces; 1 head radicchio, torn; 1 romaine lettuce heart, torn