Step 1

Set sous vide to 139-degrees.

Step 2

Slide the pork tenderloin into a FoodSaver bag and seal using a vacuum sealer. Alternatively, you can use a ziploc bag and the water displacement method.

Step 3

Place the bag in the water bath, making sure not to block the intake or output sections of the sous vide, and cook for the desired time (1 to 4 hours).

Step 4

Remove pork tenderloin from bag and place on a paper towel-lined plate. Pat it very dry with paper towels then season again with salt and pepper.

Step 5

Heat oil in a large cast iron skillet over high heat.

Step 6

Once sizzling hot, add pork tenderloin and sear on one side for 30 seconds to 1 minute, until golden. Add butter.

Step 7

Flip the pork tenderloin and cook for 30 seconds to 1 minute longer, while continually spooning the butter mixture over the tenderloin. Remove from skillet and serve.