Grilled Steak Salad with Tomato Vinaigrette

Name: Grilled Steak Salad with Tomato Vinaigrette
Ingredients: 1 pound hanger, skirt, or flank steak; 1 teaspoon kosher salt plus more; Freshly ground black pepper; 1 medium tomato (about 6 ounces), halved; 1 tablespoon minced shallot; 1 tablespoon red wine vinegar; 1/4 cup plus 5 teaspoons olive oil, divided; 4 spring onions or 6 scallions, bulbs halved, dark-green parts discarded; 5 1/2-inch-thick slices ciabatta; 8 cups mixed summer lettuces (such as mizuna, baby mustard greens, and tatsoi); 3/4 cup fresh basil leaves, torn into 1/2-inch-strips