Preheat the oven to 250°F. Slice the tomatoes in half lengthwise and transfer them to a baking sheet. Toss with the olive oil, garlic, herbs, sugar, salt, and pepper. Arrange them in a single layer, cut-side up. Bake for 2 to 2 1/2 hours, until they are very soft and juicy. Serve warm or at room temperature, garnished with fresh basil if you like.