Let the Tri Tip steak come up to room temperature, then pat the surface dry with paper towels. Rub the salt and pepper on the surface of the meat
Start the immersion circulator and bring it to 137 degrees F (for medium done), or two degrees above the desired internal temperature for the level of doneness you prefer. Seal the steak in a vacuum sealing package so that it is water-tight and will be protected from the immersion bath
Once the immersion circulator is at temperature, insert the probe of the thermometer into the meat through the sealed package. Use sous vide tape to seal around the probe so water can’t penetrate. Lower the package of steak into the water, making sure there is clearance on both sides and no part of the package touches the heating element
Cook the Tri Tip steak sous vide for about 75 to 90 minutes, depending on the thickness of the cut. Watch the thermometer or set an alarm so you know when it hits the 135 degrees F mark for medium done. Take the package out of the immersion circulator, then immediately put it in a bowl of ice water to chill it for at least 5 minutes, but no longer than 10 minutes
Heat your cast iron pan on the stove with a tablespoon of high-heat oil with a neutral flavor, such as avocado or peanut oil. Alternately, heat your grill to a 350-degree F level. Open the package holding the steak and place the meat on the pan or grill. Sear it for about three to five minutes on each side, or just until color and texture appear on the surface. Remove from the heat and slice and serve immediately