Sous Vide Flat Iron Steak

Sliced flat iron steak on a cutting board.

This easy sous vide flat Iron Steak is cooked medium-rare and is so tender and full of flavor. Choose your favorite store-brand of beef seasoning rub or do a custom seasoning according to your taste preference.

5 from 6 votes

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Prep Time: 5

Cook Time: 1 30

Additional Time: 1

Total Time: 2 35

Servings: Servings

Calories: 354kcal

Author: Pat Nyswonger

Ingredients

1-½ to 2 pounds flat iron steak
2-3 tablespoons dry beef rub

To Sear the Steak

high smoke point oil such as safflower or refined avocado oil
1 tablespoon butter

Instructions

Prepare the sous vide system:

Fill the sous vide water container with water, attach the heating unit, and set it to your desired temperature. We set our unit to 130°F for medium-rare. You should choose the temperature that you like your steak cooked to.

Prepare the Steak:

Pat the steak dry with a paper towel.
Coat the flat iron on both sides with the rub, rubbing it into the surface. (we used our Santa Maria Rub)
Transfer the steak to the refrigerator for one hour so the rub can penetrate into the steak. (this is an optional step).
Place the flat iron steak in a vacuum-seal bag and seal, removing the air. Optionally, submerge a ziplock bag in water (without submerging the opening) and let the water push all the air out, then seal the bag.

To Cook the Steak:

When the water in the sous vide container reaches your desired temperature, submerge the sealed bag into the water and cook for 1-½ hours.
Once the steak has cooked for 1-½ hours you can leave it submerged in the water container for another hour or two. It will not continue to cook but will give you plenty of time to put the rest of your dinner together.
Finishing/Searing the Steak:We have listed two methods to use when you are ready to finish/sear the steak: either a stove top or a grill. To get a good exterior color without cooking the steak further, you will need the heat to be super-hot. Work quickly, turning the steak every 15 to 30 seconds until you get a deep, rich crust.
When you are ready to sear the steak, remove the bag from the water and transfer the steak to a thick pad of paper towels. Pat the steak with paper towels to remove the surface moisture.

To Finish the Steak on the Stovetop:

Set a heavy-bottomed skillet, such as cast iron, over high heat. Add 1 or 2 tablespoons oil to the skillet, and when it is just beginning to smoke, place the steak in the skillet.
Sear the steak for 15 to 30 seconds, flip it over, and sear for 15-30 seconds. Continue searing each side, turning it over until you have a rich brown crust.
Adding a tablespoon of butter during the last 15-30 seconds will help give a good color and rich flavor to the steak. Do not add the butter sooner, or it will burn and turn bitter.

To Finish the Steak on a Grill:

To sear the steak on a grill, prepare a charcoal or gas grill for high heat. Keep the lid closed for 15 to 20 minutes so the grill grates have time to get super hot.
Cook the steak, turning every 15 to 30 seconds until a rich crust forms on the steak.

Notes

When you slice the steak, it will look as though the steak is overcooked, do not fear! This is a feature of sous vide cooking, and it is only temporary. As the sliced meat sits at room temperature and is exposed to the oxygen in the air, it will begin to "bloom" as the myoglobin in the meat comes in contact with the oxygen. The color gradually turns pink and then red, so that it might appear even more rare than it actually is.
In order to achieve a good sear and dark crust it is essential to remove any moisture from the surface before the sear. If the steak is wet then it will steam instead of sear.
A super-high heat is needed for the sear so you can get a rich color very quickly without further cooking the steak.
Turning the steak every 15-30 seconds for 1-½ to 2 minutes total will prevent overcooking while getting a rich crust.
Be sure to open windows and turn on the vent if you are using the stovetop to finish the steak.
If you are using the charcoal grill leave the steak in the water container until the charcoal is lit, spread, and the grill is hot.
The steak does not need a ‘rest’ time after it has been seared.

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