Wash tomatoes and pat dry. Cut tomatoes in half crosswise. Place cut-side-up in a shallow, heat-resistant, non-metallic, baking dish.
Dot each tomato half with about 1/2 tablespoon butter.
In a small bowl, combine remaining ingredients. Top each tomato half with some of the cheese mixture. Heat, uncovered, in Microwave Oven 5 to 6 minutes, or until tomatoes are soft and topping begins to melt. Do not overcook as tomatoes will become too soft. Serves 4 to 8
Variation: If desired, dry seasoned bread crumbs may be substituted for all or part of the Parmesan cheese.