Preheat oven to 450 degrees F. Line a roasting pan with foil. Fit it with a rack and lightly grease the rack with 1 teaspoon avocado oil.
In a small bowl, use a fork to mix together the kosher salt, black pepper, garlic powder, oregano, cumin, thyme and smoked paprika.
Sprinkle the seasoning mixture all over the pork tenderloin, then use your hands to rub it in, making sure it adheres.
Heat a large skillet over medium-high heat, about 2 minutes. Add the avocado oil and brush to coat. Gently place the pork tenderloin in the hot skillet. Sear 2 minutes on the first side, without moving, to form a nice well-browned crust.
Use tongs to gently flip to the other side, and sear 2 minutes on that side as well. Finish by searing the two remaining sides, 1 minute each.
Turn the heat off. Use tongs to transfer the seared pork tenderloin to the prepared roasting rack. Place in the hot oven and roast until an instant-read thermometer registers 145 degrees F (medium), 20-30 minutes. If roasting for longer than 20 minutes, cover the pork loosely with foil to prevent the top from burning.
Remove the pork tenderloin from the oven. Loosely cover it with foil and allow to rest for 10-15 minutes before slicing and serving.
As an alternative to searing in a skillet then roasting in a pan on a rack, you can also sear the meat in an ovenproof skillet, then transfer the skillet to the oven for roasting.