Preheat the oven to 350 degrees F (175 degrees C).

Season 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 pork loin on all sides in the hot oil, about 10 minutes total. Remove pork loin from the pan, and set aside. Pour in white wine, and bring to a simmer, stirring to dissolve caramelized bits in the pan.

Scatter butternut squash and onion in the skillet and place the browned pork loin on top so they work as a roasting rack. Stir applesauce, mustard, soy sauce, sugar, and cinnamon together in a bowl. Pour over 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