These quick-cooking broiled tomatoes make a hearty main dish when served with a salad and bread. Raclette is a mild melting cheese from the French and Swiss Alps that’s rich, creamy, gooey, and grillable. Make things easy on yourself: Shred the cheese when it’s cold and firm. And be sure to choose small tomatoes that are uniform in size.
Preheat broiler, and place oven rack 4 inches from top of oven. Coat baking sheet with cooking spray.
Arrange tomato halves cut-sides up on prepared baking sheet. Spread mustard on tomatoes, and top with cheese.
Combine breadcrumbs, capers, chives, butter, and cayenne pepper, if desired, in small bowl. Sprinkle breadcrumb mixture over tomatoes. Broil 2 to 3 minutes, or until cheese is bubbling hot and starting to brown.