Allow tenderloin to rest until it reaches room temperature. This could take about 45 minutes. Preheat the oven to 300 degrees. Salt and pepper the roast liberally. Spread 2 tablespoons of butter on the roast. Place the roast on a rack on top of a baking sheet. Bake 20 to 25 minutes per pound for rare, medium rare it should take between 30 to 35 minutes per pound. Check temperature with a thermometer. If you are not using a rack be sure to flip the roast over when cooking.
When you remove the roast heat 2 tablespoons of butter in a skillet over medium-high heat. Sear all sides of the roast in the butter until the sides brown. Allow the roast to rest for 15 minutes before serving.