Set sous vide precision cooker to 140°F (60°C).
Inspect pork tenderloin for visible excess fat, removing thick layers with a sharp boning or chef’s knife. Leave a thin layer of fat for flavor and moisture retention.
Evenly sprinkle seasoning salt, granulated onion and garlic, and black pepper over the entire tenderloin.
Place seasoned pork into a vacuum-sealed bag or heavy-duty zipper-lock bag for airtight sealing.
Submerge sealed bag in preheated water bath and cook for 1 hour.
Preheat oil in a pan to high heat; remove tenderloin from bag and pat it dry with paper towels.
Sear each side for 1-2 minutes until a golden brown crust forms.
Allow tenderloin to rest briefly before slicing into medallions.
