Preheat your oven to 450°F. Line a roasting pan with foil. Fit it with a rack and lightly grease the rack.
In a small bowl, use a fork to mix the kosher salt, black pepper, garlic powder, oregano, cumin, thyme, and smoked paprika.
Sprinkle the seasoning mixture all over the pork, then use your hands to rub it in, making sure it adheres.
Heat a large skillet over medium-high heat for about 2 minutes. Add the avocado oil and swirl to coat. Gently place the pork in the hot skillet. Sear for 2 minutes on the first side, without moving, to form a well-browned crust.
Use tongs or two wide spatulas to gently flip the pork to the other side, and sear it for 2 minutes on that side. Finish by searing the two remaining sides, 1 minute each.
Turn the heat off. Use tongs to transfer the tenderloin to the prepared roasting rack. Place it in the hot oven and roast until an instant-read thermometer registers 145°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 tenderloin from the oven. Loosely cover it with foil and allow it to rest for 10-15 minutes before slicing and serving.
As an alternative to searing in a skillet and then roasting in a pan on a rack, you can sear the tenderloin in an ovenproof skillet and then transfer the skillet to the oven for roasting.
In 2011, the USDA lowered its temperature recommendation for cooking whole cuts of pork from 160°F to 145°F with a 3-minute rest period. This change means the pork may still look pink when it reaches 145°F. That, says the USDA, is OK.
You can keep the leftovers in the fridge, in an airtight container, for 3-4 days. They can dry out when reheated, so reheat them gently, covered, in the microwave at 50% power.