Bring a small pot of water to a boil. Score the skin on the bottom of each tomato with a two-inch X. Place the tomatoes in the boiling water and cook just until the skins loosen, 30 to 45 seconds. Transfer the tomatoes to a large bowl of ice water to cool. Using a paring knife, peel off the skin. Cut off the top inch of each tomato. Using a spoon, scoop out the seeds and pulp to make a large cavity. Season with salt and pepper.
In a large bowl, whisk the EVOO, lemon juice, garlic, Dijon and crushed red pepper. Add the beans, tuna, onion, celery, parsley and tarragon; season and toss to combine. Fill the tomatoes with the tuna mixture. Sprinkle the tomatoes with the crushed grissini and drizzle with olive oil.