Season the pork loin with garlic powder, salt, and pepper. Heat olive oil in a large oven-proof skillet or Dutch oven over medium-high heat. Brown the pork loin on all sides in the hot oil, about 10 minutes total. Remove the pork loin from the pan, and set aside. Pour in the white wine, and bring to a simmer, stirring to dissolve the caramelized bits in the pan.
Scatter the butternut squash and onion in the skillet and place the browned pork loin on top so they work as a roasting rack. Stir together the applesauce, mustard, soy sauce, sugar, and cinnamon. Pour over the pork loin, then cover the pan with a lid or a double layer of aluminum foil.
Bake pork loin in preheated oven until it has reached an internal temperature of 145 degrees F (63 degrees C), about 1 hour. Allow to rest for 10 minutes before serving