Preheat the oven to 375°F. Pat the pork loin dry and season with salt, pepper, garlic powder, and onion powder.
Heat butter in a large skillet over medium-high heat. Sear the pork loin on all sides until golden brown.
Transfer the pork to a roasting pan and place in the oven. Roast for 40 minutes.
In a saucepan, combine apple cider, brown sugar, Dijon mustard, and apple cider vinegar. Simmer over medium heat until slightly thickened.
Brush the glaze over the pork during the last 10 minutes of roasting. Continue to cook until the pork reaches an internal temperature of 145°F.
Remove from the oven and let the pork rest for 10 minutes before slicing and serving.