Potato Gratin with Sweet Peppers and Tomatoes | America's Test Kitchen

Ingredients

• 2 large cloves garlic , peeled and smashed
• 2 1/2 tablespoons olive oil
• 1 medium onion , sliced thin
• 2 pounds all-purpose potatoes , peeled and sliced 1/8-inch thick or less
• Pinch cayenne pepper (optional)
• 1 1/2 cups water
• 1/2 cup dry vermouth
• 3 tablespoons minced fresh basil leaf
• 1 red bell pepper , cored, seeded, and sliced thin
• 5 plum tomatoes , sliced thin
• 1/4 cup grated Parmesan cheese