Charring the tomatoes to remove the skins gives this soup a smoky flavor.
Using a grilling fork, roast tomatoes over medium-hot coals or on a gas grill until skins blacken and split; then peel, core, seed, and chop.
In a small stockpot over low heat, melt butter with oil. Add garlic and cook until golden. Add onion and cook until slightly softened, about 5 to 10 minutes. Add carrots, celery, and 1 tablespoon chopped rosemary, and season lightly with salt and pepper. Cover pot and cook until vegetables are soft, about 15 minutes. Do not allow to brown.
Increase heat to medium and add tomatoes. Cook for 10 minutes, stirring occasionally, until mixture resembles a thick sauce. Add bread pieces and stock and bring to a simmer. Add sugar and remaining chopped rosemary. Simmer, uncovered, for 20 minutes.
Let soup cool for a few minutes, then puree in a blender until smooth. Thin with more stock if necessary. Adjust seasonings and serve hot, garnished with rosemary sprigs and creme fraiche or sour cream.