Gremolata is a parsley and lemon peel mixture commonly used in Italy with osso buco.
Heat oil in heavy large Dutch oven over medium heat. Add chopped fennel bulb; sauté until tender but not brown, about 6 minutes. Add drained tomatoes; sauté 5 minutes. Add reserved tomato juices, stock and lemon juice. Cover; simmer 15 minutes. Puree soup in blender in batches until smooth. Return to pan. Season with salt and pepper. (Can be made 1 day ahead. Cover and refrigerate.)
Mix all ingredients in small bowl.
Bring soup to simmer. Ladle into bowls. Stir spoonful of gremolata into each bowl and serve.