Step 1

Heat the oven and pan. 10 to 20 minutes before you plan to cook, place a large cast-iron or ovensafe skillet on the middle rack in the oven and heat the oven to 450°F. The skillet will heat along with the oven.

Step 2

Season the pork. Pat the pork dry with paper towels and trim off any large pieces of surface fat. Mix any spices being used with the salt and pepper in a small bowl. Rub the spice mix onto the pork on all sides.

Step 3

Swirl the pan with oil. Using oven mitts, carefully remove the hot pan from the oven. Add the oil and swirl to coat the bottom of the pan.

Step 4

Roast the pork for 10 minutes. Place the pork in the pan. (It's fine if your pork tenderloin is a little long for the pan; just bend it to fit as we did here.) Return the pan to the oven and roast for 10 minutes.

Step 5

Flip the pork, reduce the heat, and roast another 10 to 15 minutes. Flip the pork. Reduce the oven temperature to 400°F and continue roasting 10 to 15 minutes more. The pork is done when its internal temperature registers 140°F to 145°F in the thickest part, 20 to 25 minutes total.

Step 6

Rest for 10 minutes before serving. Transfer the pork to a clean cutting board, tent loosely with aluminum foil, and let it rest for 10 minutes before slicing crosswise. For extra-thin slices for sandwiches, cool the pork completely, then refrigerate before cutting.