Preheat the oven: Preheat the oven to 350°F.
Prepare the figs: In a medium saucepan, combine the sliced dried figs, sherry, and enough water to just cover the figs. Bring to a boil, then remove from the heat and set aside while you prepare the pork. (If using fresh figs, simply quarter them and set aside. They do not need to be simmered.)
8 dried mission figs, sliced, ¼ cup dry sherry
Sear the pork: Pat the pork tenderloin dry and season generously with salt and pepper. Heat 2 tablespoons of the oil in a large oven-safe skillet over medium-high heat. Sear the pork on all sides until nicely browned, about 6 to 8 minutes total, adding a little more oil if needed.
1 pound pork tenderloin, ½ cup light olive oil
Add the figs: Pour the fig mixture and its cooking liquid (or the fresh figs, if using) around the pork. Drizzle in the remaining oil, adjusting the amount to your preference. Lay 2 rosemary sprigs over the pork.
2-3 rosemary sprigs
Roast the pork: Transfer the skillet to the oven and roast for about 25 minutes, or until the thickest part of the pork reaches 145°F on an instant-read thermometer. Remove the pork to a plate and tent loosely with aluminum foil to rest.
Cook the onions: Add the sliced red onion, crushed garlic, and remaining rosemary sprig to the skillet with the figs and pan juices. Return the skillet to the oven and roast for about 15 minutes, stirring once or twice, until the onions are tender and caramelized. If desired, place the pork back on top of the onion mixture during the last 5 minutes to warm through and absorb additional flavor.
1 large red onion, 4 garlic cloves, salt and pepper to taste
Slice and serve: Slice the rested pork tenderloin across the grain and serve topped with the fig, onion, and rosemary mixture along with plenty of the flavorful pan juices.