Preheat oven to 275 degrees.
Arrange tomatoes on a sheet pan, cut side up, in a single layer. Drizzle with olive oil and balsamic vinegar.
Sprinkle with garlic, sugar, 1 1/2 teaspoon of salt and 1/2 teaspoon pepper. Roast for 2 hours until the tomatoes are concentrated and begin to caramelize. Allow tomatoes to cool to room temperature.
Cut the mozzarella into slices slightly less than 1/2 inch thick. If the slices of mozzarella are larger than the tomatoes, cut them in half so they are approximately the same size. Layer the tomatoes alternately with the mozzarella on a platter and scatter the basil on top. Sprinkle lightly with salt and pepper and drizzle with olive oil ( I didn't do this cuz I didn't want the extra calories and it was still fabulous ). Serve at room temperature.