Cut veal into large, bite-size cubes. Peel turnips, quarter and cut into pieces. Rinse and slice scallions. Peel and chop garlic. Drain anchovies, pat dry and chop.
Heat butter in a roasting pan, add vegetables, including garlic, anchovies and lemon peel. Cover and sauté for 5 minutes.
Add veal and deglaze with tomato puree. Season with salt, pepper and paprika. Cover and simmer, stirring occasionally, over low heat for 30-40 minutes. Add cognac during the last 10 minutes of cooking.
Meanwhile, boil pasta in plenty of salted water until al dente, then drain.
Stir cream into sauce and bring to a boil. Season with tarragon, salt and pepper. Remove from heat and let sit for 5 minutes.
Place pasta in bowls and top with sauce. Serve garnished with scallions and tarragon.