Preheat the oven to 400°F.
Butterfly the pork tenderloin by making a deep cut to the middle of the loin along the full length of the meat, leaving at least ½" intact at the bottom. Open the meat like a book, cover with plastic wrap and pound it slightly with a mallet or rolling pin.
Season the inside with salt and pepper and spread the goat cheese over one half of the meat, close to the centre opening. Lay the pears on top of the cheese, close up the meat and tie it together with kitchen string, making knots every 2”. Season the outside of the meat with salt and pepper and set aside.
Place a large ovenproof skillet over medium heat and add olive oil and butter. When the butter has melted, sear the tenderloin on all sides until well browned. Transfer the skillet to the oven and cook the meat for 15–20 minutes, or until it reaches an internal temperature of 155–160°F.
Remove the meat from the oven and place it on a plate. Cover with tin foil and allow to rest for 5 minutes. Meanwhile, set the skillet over medium heat and whisk in the balsamic vinegar, mustard, and maple syrup, taking care to scrape up the browned bits from the bottom of the pan. Add the cranberries and rosemary and bring the liquid to a low boil. Cook until sauce is thick and syrupy and the cranberries have burst. Season with salt and pepper.
Slice the pork tenderloin and lay it on a platter. Spoon the glaze over the top of the meat and serve.