Gratin of Red and Yellow Peppers and Tomatoes Recipe

Ingredients

• 1 1/2 lb red bell peppers (3 large), halved lengthwise
• 1 1/2 lb yellow bell peppers (3 large), halved lengthwise
• 5 tablespoons extra-virgin olive oil plus additional for oiling pan
• 1/2 cup finely chopped fresh flat-leaf parsley
• 1 tablespoon finely chopped fresh thyme
• 1/2 teaspoon finely chopped fresh rosemary
• 1 teaspoon finely grated fresh lemon zest
• 1 1/2 teaspoons salt
• 3/4 teaspoon black pepper
• 3 1/2 cups cubed (1/2-inch) baguette (preferably sourdough; from 1 loaf)
• 1 oz finely grated Parmigiano-Reggiano (1/2 cup)
• 4 large yellow tomatoes (2 lb total), cored and each cut crosswise into 5 slices
• 4 large red tomatoes (2 lb total), cored and each cut crosswise into 5 slices
• a 13- by 9-inch (3- to 31/2-qt) gratin or nonreactive shallow baking dish (see cooks' note, below)