• About 30 minutes before cooking, allow the meat to rest at room temperature for 30 minutes. This will prevent dry, tough meat.
• Preheat the oven to 450°F degrees.
• In a small bowl, mix together the garlic powder, onion powder, sage, salt, and paprika. Whisk to combine.
• Sprinkle the rub on all sides of the pork tenderloin, turning and pressing the mixture into the meat so it adheres well. (Do this in a 9x13 casserole dish for easier clean-up!)
• In a large cast iron skillet, melt one tablespoon of butter with the olive oil over medium-high heat.
• Once hot, add the tenderloin to the skillet and sear on each side (about 3 minutes each side), until golden brown. This should take about 5-8 minutes total.
• After searing, turn the stove off. Add the garlic cloves, 3 tablespoons of butter, and rosemary sprigs to the skillet. Place the skillet in the oven (uncovered) and roast for 10 minutes.
• After 10 minutes, remove from the oven and transfer the pork tenderloin to a cutting board with a well or a serving platter. Allow the meat to rest at room temperature for 10 minutes, or until the internal temperature reaches your desired doneness when read with a meat thermometer.
• While the pork tenderloin is resting, make the pan sauce (optional).

To Make the Pan Sauce:

• Without cleaning the cast iron skillet, add 2 tablespoons of butter to the skillet with the rosemary sprigs still remaining in the pan. (the pork tenderloin should be resting on a separate dish).
• Gently melt the butter in the hot pan and scrape up the browned bits from the bottom of the skillet with a wooden spoon. Remove the rosemary stems when the sauce is complete.
• After the pork tenderloin has rested for 10 minutes (or reaches desired doneness), slice the meat into ½-inch thick slices and serve with the sauce drizzled over the top.