Iceberg Wedges With Bacon And Buttermilk Dressing

Name: Iceberg Wedges With Bacon And Buttermilk Dressing
Ingredients: 4 large plum tomatoes, bottoms marked with an X; 1/4 cup extra-virgin olive oil; 1 teaspoon finely chopped thyme; Salt and freshly ground pepper; 2 ounces brioche, cut into 3/4-inch cubes (2 cups); 1/3 cup mayonnaise; 1/4 cup crème fraîche or sour cream; 1/4 cup buttermilk; 2 1/2 tablespoons fresh lemon juice; 1 tablespoon chopped flat-leaf parsley; 1 1/2 teaspoons chopped mint; 3 tablespoons snipped chives; 1/2 pound thickly sliced bacon, cut into 2-by-1/2-inch pieces; 2 medium heads of iceberg lettuce, cut into 4 wedges each