MAKE THE TENDERLOIN: In a small bowl, combine the fennel, salt, pepper, chili powder, and cinnamon. Pat the spice mix all over the tenderloin.
In a large heavy-bottomed skillet, heat the olive oil over medium heat. Add the tenderloin and sear on all sides until browned, about 1 1/2 minutes per side. Transfer the pork to a baking dish and set aside.
In a small saucepan, toast the star anise over medium heat to allow the flavor open up, about 1 minute. Add the brown sugar, maple syrup, and garlic, stir to combine, and cook until the sugar melts and the glaze begins to bubble, 4 to 5 minutes. Remove from the pan from the heat and let sit for 1 hour to let the glaze thicken and the flavors meld.
Preheat the oven to 375°F. Brush the tenderloin evenly all over with about one third of the glaze. Bake the tenderloin, basting every 5 minutes or so with more of the glaze, for 15 to 20 minutes, until an instant-read thermometer inserted in the center reaches 160°F.
Transfer the tenderloin to a carving board and tent with foil (do not clean the pan or discard any of the glaze). Let the meat rest while you roast the fruit.
Increase the oven temperature to 425°F.
MAKE THE FRUIT: In a medium bowl, toss the pears with the shallot, 2 tablespoons of the sugar, the thyme, lemon zest, star anise, a good pinch of salt and a crack of pepper. Spread the mixture over the bottom of a rimmed baking sheet and roast until the pear is just tender, 8 to 10 minutes, add the plums, the remaining 1 teaspoon of sugar, and lemon juice, toss, and roast for 1 minute more.
Cut the pork into 1-inch thick medallions and arrange them on a platter with the fruit. Drizzle with a couple of spoonfuls of any glaze left in the saucepan and serve.
