Preheat oven to 400°F. Let the pork sit out and come to room temperature for about 30-45 minutes.
Whisk together the applesauce, brown sugar, Dijon mustard, Worcestershire sauce, vinegar, and rosemary or thyme. Divide the mixture between two bowls (you will use half to baste the meat while it’s in the oven, and the other half to baste the meat at the very end).
Pat pork dry; season liberally on all sides with salt and pepper. Heat oil in a 10- to 12-inch cast iron skillet (or other oven-proof skillet) over medium-high heat until the oil is shimmering. Sear the pork on two sides (about 4-6 minutes per side), just until a nice golden-brown color develops and the meat releases easily from the pan. You don’t need to cook the meat all of the way through, since it will finish in the oven.
Transfer the pork (fat side up) to the oven and roast for 45-50 minutes, or until an instant-read thermometer inserted into the thickest part of the pork reads 145°F. Baste the top and sides with the applesauce glaze after the first 25 minutes. You will probably not use all of the glaze (discard any extra). Exact cooking time will vary depending on the size of your pork.
Baste again with the reserved applesauce glaze at the very end. Cover loosely with foil and allow the meat to rest for at least 10 minutes before thinly slicing and serving.
Notes
If you don’t have a cast iron skillet (or other oven-proof skillet), sear the pork in a skillet and then transfer the meat to a roasting pan or other oven-safe dish to finish in the oven. If you're in the market for a new skillet, be sure to check out our recommendations for the 7 best cast iron skillets.
Before the pork goes into the oven, make sure that the thin layer of fat is on top. This allows the fat to drip down over the meat as it roasts, keeping the pork loin nice and juicy.
Cook the pork roast uncovered, which allows for extra browning on the outside of the meat. The applesauce glaze adds flavor and also helps to keep the pork moist and juicy.
The total cooking time will vary depending on the size, thickness, and temperature of your pork when it goes into the oven. As a result, it’s best to use a meat thermometer to know exactly when your pork reaches the desired temperature.
Allow the meat to rest before slicing and serving. This will allow the juices to redistribute, rather than just running onto the cutting board.
Garnish with chopped fresh herbs for a bright, colorful touch at the end.