Serve these tomatoes as an antipasto or as a vegetable side dish.
Heat oven to 375 degrees. Using a sharp knife, cut a very thin slice from the bottom of tomatoes to enable them to stand upright. Cut 1/8 inch from the stem end of each tomato; discard ends. Use a melon baller to scrape flesh, seeds, and juice from 6 of the tomatoes into a medium bowl. Repeat with remaining 2 tomatoes, but scrape the flesh, seeds, and juice into a separate bowl.
Sprinkle a bit of salt to taste in each tomato; stand them in a small baking dish.
To the reserved pulp of the 6 tomatoes, add 1 teaspoon salt, basil, finely chopped tarragon, shallots, pepper, and arborio rice; mix to combine.
Fill tomatoes with rice mixture, gently tapping the bottom of each tomato to distribute filling evenly. Sprinkle Parmesan over the tops and drizzle with olive oil.
Add wine to the reserved pulp of the 2 tomatoes, mix to combine, and pour into the bottom of the dish.
Bake until the tops are golden brown and the rice is tender, 45 minutes to 1 hour. Remove from oven and serve immediately. Garnish with remaining teaspoon chopped tarragon.