Preheat an outdoor pellet smoker to 225 degrees Fahrenheit (107 degrees Celsius).
Rub a 3 to 4 pound pork loin with 1 tablespoon olive oil on all sides. Season with spice mixture and rub on all sides.
In a small bowl, mix together 1 1/2 tablespoons salt, 1 1/2 tablespoons black pepper, 1 tablespoon smoked paprika, 1 tablespoon onion powder, and 1/2 tablespoon garlic powder.
Place loin on the smoker. Close the lid and smoke until the internal temperature of the pork reaches 135℉, which will take approximately 90 minutes to 2 hours, depending on the thickness of your pork loin. Use a meat thermometer or internal probe for accuracy.
Remove the pork loin from the smoker and transfer to a large baking sheet. Loosely wrap in aluminum foil.
Increase the smoker temperature to 400 degrees Fahrenheit (204 degrees Celsius). Melt 4 tablespoons salted butterWhen the smoker reaches temperature, return the pork loin to the smoker.
Use the melted butter to baste the loin and cook until the internal temperature reaches 145 degrees Fahrenheit (63 degrees Celsius), about 10 to 20 minutes.
Remove the pork loin from the smoker and let it rest for 5 to 10 minutes before slicing and serving.
Notes
For a sweet and fruity smoke, go with fruitwood pellets like apple or cherry. If you’re after that classic Southern barbecue flavor, hickory pellets are the way to go.