Season all sides of the tenderloin with Italian seasoning, salt, and pepper.
Heat oil in a large heavy-bottomed skillet, such as cast iron, over high heat.
Add the pork to the skillet and sear for 2-3 minutes per side.
Transfer skillet to the oven and bake for 15 minutes or until the pork reaches an internal temperature of 145 degrees.
Remove from oven and let rest for 5 minutes.
While pork is resting, whisk together the butter, garlic, onion powder, and parsely.
Pour the garlic butter over the pork.
Slice pork into 1-inch thick slices and serve.
Notes
If you don't have an oven safe skillet, transfer from the skillet to a baking dish and proceed with baking.Pork is safe to eat while still pink in the center. It does tend to dry out quickly when cooked well done, so we recommend cooking to 145 degrees so that the pork is juicy and tender.