Step 1

Place a 10-inch cast iron skillet in the oven on a middle rack and heat the oven to 450 degrees F (230 degrees C). The skillet will heat along with the oven.

Step 2

Using oven mitts, remove the skillet from the oven and add olive oil to the pan. Give the pan a swirl so that the oil coats the entire bottom.

Step 3

Mix together the Italian seasoning, sage, garlic powder, salt, and black pepper in a small bowl. Sprinkle the seasoning mix over both sides of the turkey and rub the spices in with your fingers.

Step 4

Place the tenderloin in the skillet and using oven mitts, return the skillet to the oven and bake for 10 minutes.

Step 5

After 10 minutes, remove the skillet from the oven and using tongs, flip the turkey over. Reduce the oven temperature to 400 degrees F (200 degrees C) and continue roasting another 15 minutes.

Step 6

Remove the skillet from the oven. Add butter to the top of the turkey and cover the skillet with a large plate, a pan lid, or foil. Let the turkey rest for 15 minutes before serving. The turkey is done when its internal temperature registers 165 degrees (74 degrees C) in the thickest part of the meat.

Step 7

Remove the foil. Slice and spoon the butter sauce over the turkey. Enjoy hot.