Working in a blender in 2 batches, puree the tomatoes with the vegetable broth, olive oil, tomato paste, red wine vinegar and sugar until very smooth. Transfer to a bowl, season with salt and pepper and refrigerate until chilled, about 2 hours.
In a small bowl, mix the crème fraîche with the chopped tarragon and season with pepper. Ladle the soup into bowls. Top with a dollop of the crème fraîche, garnish with the tarragon leaves and serve.