- 1 tablespoon unsalted butter
- 1 teaspoon olive oil
- 1 (1-pound) boneless Muscovy duck breast with skin or 2 (7- to 8-ounce) Long Island (also called Pekin) duck breast halves with skin
- 1/2 medium onion, chopped
- 1 garlic clove, smashed
- 1 teaspoon chopped rosemary
- 1/2 cup dry red wine
- 2 cups rich chicken stock or reduced-sodium chicken broth
- 1 (14- to 15-ounce) can whole tomatoes in juice, drained, reserving juice, and chopped
- 1/2 pound dried egg tagliatelle or egg fettuccine
- Heat butter and oil in a deep 10-inch heavy skillet over medium heat until foam subsides.
- Meanwhile, pat duck dry and sprinkle with 1/4 teaspoon each of salt and pepper.
- Sear duck, skin side down, until golden brown and some of fat has rendered, about 6 minutes. Turn over and cook until browned, about 2 minutes more. Transfer duck to a plate, then add onion to fat in skillet with garlic, rosemary, and 1/8 teaspoon salt and cook, stirring occasionally, until onion is softened and golden brown, about 6 minutes. Add wine and boil 3 minutes.
- Return duck, skin side up, to skillet, then add any juices from plate, stock, and tomatoes with their juice. Bring to a boil, then gently simmer, covered, 1 hour.
- Transfer duck to a cutting board, then skim off about three fourths of fat from sauce and discard.
- Purée sauce in batches in a blender (use caution when blending hot liquids). Return sauce to skillet and boil, stirring occasionally, until reduced to about 2 1/2 cups, about 8 minutes.
- While sauce reduces, finely chop duck with skin.
- Return chopped duck to sauce and season with salt and pepper.
- Cook tagliatelle in a pasta pot of boiling salted water (3 tablespoons salt for 6 quarts water) until al dente, then drain pasta and toss with duck ragú.