Spicy Tomato Granita

Bring a large pot of water to a boil. Fill a large bowl with ice water. Using a sharp knife, make a shallow X in the bottom of each tomato. Add the tomatoes to the boiling water and blanch just until the skins begin to pull away, about 20 seconds. Using a slotted spoon, immediately transfer the tomatoes to the ice water. Drain and peel the tomatoes. Halve the tomatoes crosswise. Squeeze the seeds into a sieve set over a bowl. Press on the seeds to extract the juice; discard the seeds. Cut the tomatoes into large chunks. In a food processor, puree the tomatoes with the tomato juice, cilantro, lime juice and chile until smooth. Season with salt. Spread the tomato mixture in a shallow 9-by-13-inch glass baking dish. Freeze until set around the edges, about 1 hour. Using a fork, scrape the ice crystals into the center and freeze again. Repeat the scraping every 30 minutes until the entire mixture has turned into ice flakes, about 2 hours longer. Serve the granita in glasses garnished with the tarragon sprigs.