• Preheat oven to 400 degrees.
• Score the pork fat with a sharp knife, making an X pattern.
• In a small bowl, combine the vinegar, olive oil, brown sugar, garlic powder, thyme, salt, and black pepper. Whisk to combine, then coat the entire pork loin with the mixture.
• Place chopped onions and apples on the bottom of a roasting pan, pour in ½ cup chicken broth, and place the pork loin on top of the mixture with the fat cap facing up.
• Roast the pork loin in the preheated oven for 1 hour, or until the internal temperature reaches 145 degrees. Then remove the pork from the oven and let it rest on a cutting board.

Gravy

• Pour the pork drippings, apple chunks, and onion into a saucepan and mash the mixture together. Set over medium-low heat, then add butter, brown sugar, and whisk in flour. Continue cooking for two minutes, while whisking.
• Slowly add chicken broth, while whisking, to ensure it fully incorporates. Then bring the gravy to a simmer. Once thickened, add salt and black pepper to taste.
• Remove the gravy from the heat, and serve it over pork loin slices.