In a small bowl mix together the oil, salt, and pepper until well combined.
Pat the pork dry with paper towels then run the oil mixture evenly all over the pork.
Heat a large cast-iron skillet over medium-high heat until the skillet is hot.
When the skillet is hot lay the pork loin in the pan and sear on all sides until well browned, 2 to 3 minutes per side.
Turn the pork so its fat-side up in the skillet then place the skillet in the preheated oven until cooked through (internal temperature of 145°F), 55 to 65 minutes (15 to 20 minutes per pound).
Take the pork out of the oven and let rest for about 20 minutes before slicing and serving.