Start by trimming away any fat or silver skin from the backstrap. Mix the spice rub ingredients. Sprinkle the spice rub evenly over all surfaces of the backstrap. Let the meat rest while you heat your Traeger grill to 200 degrees with the SuperSmoke function turned on.
Mix the rub ingredients, then apply to the meat’s surface.
Place the seasoned backstrap on the grill and cook until the internal temperature reaches 125 degrees. Using a premium remote thermometer like one from the Meater brand allows you to keep an eye on the temperature without repeatedly lifting the lid on your grill, releasing the smoke and heat.
Using a good wireless thermometer makes it easy to avoid overcooking the backstrap.
Once the backstrap has hit the desired temperature, move it to a warm platter and tent with foil. Place a large cast-iron skillet over high heat. Add a tablespoon of a high smoke point cooking oil like grapeseed or peanut oil. Swirl the pan around to spread the oil.
Once the oil begins to smoke, put the backstrap in the skillet. Allow the backstrap to cook for 1 minute without moving it. Flip the backstrap and repeat the process on the opposite side. If your backstrap is thick, repeat the process on the sides of the meat. Return the backstrap to the platter and loosely tent with foil again. Allow the meat to rest for 3 to 5 minutes before slicing.