Method
Preheat oven to 200°F. Wash tomatoes and cut out the stem core. Slice the tomatoes in half lengthwise. Scoop out and discard the seeds, leaving as much pulp as possible.
Place tomatoes, cut sides up, on a lightly oiled sheet tray. They can be placed closely together since they shrink considerably during baking.
Combine garlic and olive oil; spoon over tomatoes. Season with salt and pepper. Bake 6 to 8 hours or until tomatoes are reduced in size but will retain their shape.
With about a half hour left in roasting the tomatoes, sprinkle parmesan cheese over the top of the tomatoes. (Note: The time the tomatoes take to cook will vary because their size and moisture content vary.)
By the end, they are almost caramelized and crispy on the edges. Remove from oven and let cool. Increase oven temperature to 350°F.
To assemble the sandwich, toast the ciabatta bread with olive oil and garlic.
Place the tomatoes on the top and bottom of the ciabatta. Cover the tomatoes with sliced mozzarella cheese and bake in a 350°F oven until the cheese melts.
Top each half with arugula and basil leaves.
Drizzle with reduced balsamic vinegar and close the sandwich. Cut and serve at once.