Preheat oven to 350°. Set tomato halves cut side up in an oiled baking pan and spread about 1/2 tsp. pesto over each. Bake until tomato halves are browned on top and slightly shriveled, about 1 1/2 hours.
Spread pesto generously over 4 slices of bread. Top with turkey, hot tomatoes, mozzarella, arugula leaves, and remaining slices of bread. Serve with remaining pesto if you like.
Note: Nutritional analysis is per sandwich.