Heat the oven to 450°F with a rack in the middle position. In a small bowl, stir together 3 tablespoons oil, three-quarters of the garlic, 1 tablespoon orange zest, the coriander, 1 teaspoon salt and ¾ teaspoon pepper. Rub all over the pork.

In an oven-safe 12-inch skillet over medium-high, heat the remaining 2 tablespoons oil until barely smoking. Add the pork and cook, turning occasionally, until lightly browned on all sides, about 4 minutes. Transfer to a plate. In the same skillet over medium-high, combine the fennel and 2 tablespoons water. Cook, scraping up any browned bits, until lightly browned, 3 to 4 minutes. Set the pork on the fennel, then transfer the skillet to the oven. Roast until the center of the thickest part of the pork reaches 135°F or is just slightly pink when cut into, 9 to 12 minutes.

Remove the skillet from the oven (the handle will be hot), transfer the pork to a cutting board and tent with foil. To the fennel mixture in the pan, add the remaining garlic and 1 tablespoon orange zest, the orange juice and ½ cup water. Bring to a simmer over medium-high and cook, stirring, until the fennel is tender and the sauce is lightly thickened, 4 to 6 minutes. Off heat, stir in the vinegar, then taste and season with salt and pepper. Transfer to a serving dish. Slice the pork and arrange on top. Drizzle with additional oil and serve with orange wedges.

Optional garnish: Chopped fresh oregano OR flaky salt OR both