Set the Anova Sous Vide Precision Cooker to 138°F.
Place the lobster tails, butter, tarragon, and salt in a large zipper lock or vacuum seal bag. Seal the bag using the water immersion technique or a vacuum sealer on the moist setting. Place the bag in the water bath and set the timer for 1 hour.
When the timer goes off, remove the bag from the water bath. Carefully remove the lobster tails from the bag.
Place lobster on a serving platter and drizzle with melted butter from the bag. Garnish with lemon wedges. Serve.