Preheat oven to 425 degrees with the rack in the middle. Preheat a cast iron skillet over medium high heat.

In a small bowl, combine the pumpkin butter, apple sauce and thyme. Stir to combine, set aside.

Pat the pork tenderloin dry with a paper towel and season generously with salt and pepper on all sides. When the skillet is hot, add the olive oil and sear the pork loin on all sides until golden brown, about 2 minutes per side. Top with the pumpkin butter & thyme mixture and spread evenly to coat the top of pork tenderloin.

Transfer the pork tenderloin in the cast iron skillet to the oven to finish cooking. Cook until the meat is 145 degrees on an instant read thermometer, about 15 minutes, depending on the thickness of your pork tenderloin. Remove the cast iron skillet from the oven, transfer the pork tenderloin to a cutting board and allow to rest for a few minutes.

Slice the pork loin into ½" thick slices. Serve warm.

Leftovers will keep refrigerated in an airtight container for 3 days.