Preheat oven to 400 degrees F (200 degrees C).

Mix honey, Dijon mustard, and black pepper together in a bowl until texture of a paste.

Heat a cast iron skillet over medium-high heat. Cook pork loin in the hot skillet until browned on all sides, about 5 minutes. Transfer pork loin to a baking dish. Spread honey paste over entire pork loin. Spread pineapple chunks around pork loin and sprinkle salt over pork loin.

Place a cooking thermometer into the pork loin and cover dish with aluminum foil.

Bake in the preheated oven for 5 minutes. Decrease oven temperature to 375 degrees F (190 degrees C). Continue cooking until pork is cooked through, 30 to 45 minutes. An instant-read thermometer inserted into the center should read at least 145 degrees F (63 degrees C).

Transfer pork loin to a work surface and let rest, 3 to 5 minutes. Blend pineapple chunks and drippings in a blender until sauce is smooth; serve alongside pork loin.