Preheat oven to 400 degrees. Slice lengthwise into each pork chop to create a slit or pocket in the meat. Season with salt and pepper on both sides and set aside.
Heat 1 tablespoon olive oil in a large heavy oven-safe skillet over high heat. Add in diced apples, diced onion, and brown sugar. Cook until apples and onions are soft 5 to 7 minutes.
Spoon mixture into the pork chop pockets until full and wipe out pan. Use toothpicks to secure the pocket opening shut to keep the mixture inside.
Return pan to heat and add in the remaining 1 tablespoon olive oil. Once it is hot, sear pork chops in the skillet for 2 to 3 minutes per side.
Scatter red onion chunks and apple slices (if using) into skillet around the pork chops and place skillet directly into the preheated 400 degree oven. Let the pork chop finish cooking, 15 to 20 minutes, or until the pork reaches an internal temperature of 145 degrees Fahrenheit.