- 2 tablespoons vegetable oil, divided
- 1 small yellow onion, halved through root
- 1 small bunch baby turnips (about 12 ounces), greens torn into pieces, turnips peeled, quartered
- 3 large shallots, sliced into rings
- 1 3″ piece ginger, peeled, sliced 1/4″ thick
- 3 ounces kombu
- 1 tablespoon kosher salt, plus more
- 1 cup dry vermouth
- 1/2 small butternut squash (about 12 ounces), peeled, seeded, cut into 1/2″ thick pieces
- 6 4-ounce pieces skin-on salmon fillet
- Freshly ground black pepper
- 1 lemon, halved
- Heat 1 tablespoon oil in a large skillet over medium-high heat. Add onion, cut sides down, and cook, undisturbed, until dark brown, about 5 minutes.
- Transfer onion to a large Dutch oven or other large pot and add turnips, shallots, ginger, kombu, 1 tablespoon salt, and 8 cups water. Bring to a gentle simmer (do not boil or broth will be bitter) and cook until broth is light golden and onion is soft, 40–50 minutes.
- Add vermouth to broth and simmer 5 minutes. Remove onion and kombu; discard. Add squash and simmer until just softened, 12–15 minutes. Add turnip greens and simmer, stirring occasionally, until tender, about 2 minutes.
- Meanwhile, season salmon with salt and pepper. Heat remaining 1 tablespoon oil in a large skillet over medium-high heat. Cook salmon, skin side down, until skin is very crisp, about 2 minutes. Turn salmon and cook 30 seconds longer (salmon will be rare; it will continue to cook in the hot broth). Spoon broth and vegetables into shallow bowls and top with salmon, skin side up; squeeze lemon over.
- DO AHEAD: Broth and vegetables (without turnip greens) can be made 1 day ahead. Reheat and add greens just before serving.