Sous Vide Cod

Fill a large pot with water. Attach an immersion circulator to the pot. Set the temperature to 130 degrees F (54 degrees C) and the timer to 35 minutes. Season cod lightly with salt and pepper. Zest 1/2 of the lemon over each piece. Slice lemon. Place butter and 2 lemon slices over the lemon zest. Place 1/2 of the shallot slices in the bottom of a resealable bag and place 1 cod loin on top. Repeat with second piece of cod and remaining shallot slices. Close the bags, leaving 1 small corner open. Lower the bags into the water and submerge until all the air has been expelled. Close the corners. Wait until timer goes off and remove the bags. Carefully transfer cod onto 2 plates. Drizzle 1 tablespoon of cooking liquid from the bag over each cod loin. Garnish with extra lemon slices.