Use a sharp knife to trim the fat cap until only a thin layer remains (about 1/4-inch thick). You can also ask your butcher to trim it for you.

Preheat smoker to 225˚F.

In a small bowl, stir together brown sugar, salt, smoked paprika, chili powder, garlic powder, onion powder, black pepper, and ground cumin.

Rub the pork with oil all over. Spread the dry rub all on all sides in an even layer.

Place pork loin on the preheated smoker. Smoke until the internal temperature reaches about 141˚F to 143˚F. This will take anywhere from 2 to 3 1/2 hours, depending on how thick the cut of meat is. Be sure to use a meat thermometer or probe thermometer to measure the internal temperature.

Remove from the smoker and let rest on a cutting board for 15 to 20 minutes. This resting time will allow the pork to come to 145˚F.

Slice and serve warm.