Preheat the oven to 275 degrees.
Arrange the tomatoes on a sheet pan, cut sides up, in a single layer. Drizzle with the olive oil and balsamic vinegar. Sprinkle with the garlic, sugar, 1½ teaspoons salt, and ½ teaspoon pepper. Roast for 2 hours until the tomatoes are concentrated and begin to caramelize. Allow the tomatoes to cool to room temperature.
Cut the mozzarella into slices slightly less than ½ inch thick. If the slices of mozzarella are larger than the tomatoes, cut the mozzarella slices in half. Layer the tomatoes alternately with the mozzarella on a platter and scatter the basil on top. Sprinkle lightly with salt and pepper and drizzle lightly with olive oil. Serve at room temperature.
Copyright 2008, Barefoot Contessa Back to Basics by Ina Garten, Clarkson Potter/Publishers, All Rights Reserved