Add ingredients to a saucepan then bring to a boil. Turn heat down to medium-low then simmer until cranberries are tender and sauce has thickened, 10-15 minutes, stirring occasionally. Pour sauce into a bowl then chill (can be done several days ahead of time.)
For the Pork Tenderloin:
Preheat oven to 450 degrees. Season entire tenderloin generously with salt, pepper, onion powder, and dried thyme. Add enough oil to a large, oven-proof skillet over medium-high heat to thinly coat the bottom then add the seasoned tenderloin and sear on four sides until golden brown, 1-2 minutes per side. Place skillet into oven then roast for 8-15 minutes or until a meat thermometer inserted into the thickest part of the tenderloin reads 140 degrees.
Transfer tenderloin to a cutting board then let rest for a minimum of 10 minutes before slicing. Serve with Cranberry-Pear Sauce.
Notes
For an easy side dish, turn oven down to 425 degrees after removing pork tenderloin, then roast green beans tossed with extra virgin olive oil and seasonings for 10-15 minutes or until tender.