This Sous Vide Flat Iron Steak is the perfect way to cook flat iron. It’s tender with a pink finish, coated in Creole seasoning, and seared in a cast iron for the easiest and most rewarding steak you’ve had in a long time!

Above shot of flat iron, sliced to show pink center, fries and a variety of dipping sauces on a wooden background

Can a simple cut, like the flat iron, actually be a prime choice for entertaining? Turns out, yes! 

With a very simple cooking method and a liberal coating of everyone’s favorite Creole seasoning blend, we take an affordable cut of steak and turn it into gourmet food. 

This is the best flat iron I have ever had

GC Meat Labs Taste Tester

What is sous vide?

I get it. Sous vide sounds stupid fancy…and also complicated. But really sous vide cooking is just a bath of water heated to a low temp to cook steak perfectly and evenly. And hint, restaurants around the world use this technique simply because it produces consistent results.

It works amazingly on steaks, pork, chicken, and even fish! The best part is it takes a lot of the guesswork out of cooking by with simple science. By setting the temperature of the water bath, you are guaranteed to cook to the desired temp you are aiming for.

The water heats and circulates around the vacuum-sealed beef to cook it flawlessly to the temperature you program into the sous vide machine. The result is a pink edge-to-edge, evenly cooked slice of meat. Since we’re not applying an aggressive heat source, but gently cooking it with the heated water flowing around it to slowly raise the temperature, it becomes incredibly tender!

After the sous vide has run its course, then you quickly pan-sear the beef in cast iron to give it that crispy crust and it’s good to go! We do this because when beef comes out of the sous vide, altho it’s perfectly cooked, it doesn’t have that pretty crust we have come to love on our meat. It’s actually pretty darn basic!

Ingredients for flat iron steak.

What you’ll need to make this recipe:

You don’t need much to make this recipe!

Ingredients

  • Flat Iron Steak – you’ll need one 2-3 pound flat iron steak.
  • Marinade – use Tony Chachere’s Pourable Steakhouse Marinade. 
  • Seasoning – use Tony Chachere’s Original Creole Seasoning, this
  • Butter – adds moisture and flavor depth.

Equipment

In terms of the machine needed to actually do the sous vide method, you have a couple of options:

  1. Anova Circulator System (my favorite): This one can be attached to any size container, which means you aren’t limiting the size of the meat you’re working with.
  2. Sous Vide Machine: This is the entire package, countertop appliance. It’s easy to program and has the timers built-in. The only downside is it takes up precious real estate on a countertop.
  3. All-In-One Machine: A slow cooker that is also a rice cooker that is also a sous vide machine. I have the Wolf Gourmet one and it’s great.

Besides the actual circulation apparatus, you need a food-safe vacuum-sealed bag. You need to make sure the beef is vacuum-sealed because air pockets will cause the meat to float and it won’t cook evenly. A food saver is perfect for this because it comes with everything you need!

How to make sous vide flat iron steak

Marinate the steak: pour the marinade over the steak and let sit for 6-8 hours.

Flat iron steak covered in steakhouse marinade.

Prep the equipment: prep the sous vide machine according to manufacturers’ directions for 125ºF.

Prep the steak: pat the meat dry and rub with seasonings.

Sous vide process: place the steak into a food-safe sous vide bag and seal so there are no air pockets. Submerge the sealed steak into the water and set the timer for 1 hour. Once the flat iron has reached 125ºF, the sous vide is done.

Sear: take the steak and add it to a hot skillet with butter. Sprinkle on additional seasoning and sear on both sides until a crust forms.

What temperature do you sous vide steak at?

I prefer rare steak so I sous vide mine at 125ºF so once I sear it, it reaches 135ºF. 

If you prefer a more well-done steak, adjust the temperature of the sous vide to reflect your desired temp minus 5-10 degrees. The final 5-10 will be achieved when you sear!

Edge to edge pink shown on a hand held slice of flat iron.
That pink to pink edge tho….

Can a sous vide steak get a good crust?

Totally! The sous vide method gives the meat an ultra tender texture but, once it’s done, you can sear it on the stove and still achieve that crispy crust we all want in a good piece of steak.

Over head shot of sliced flat iron steak with fries, dipping sauces on a wooden board.

Recipe FAQs

Can I cook it longer/more done?

Yes, if you would like to cook the steak to medium and beyond adjust the temperature of the sous vide to reflect the desired temp minus 5-10 degrees. The final 5-10 will be achieved when you sear.

Are there substitutes for the marinade?

Yes, try Italian dressing or any mild marinade in place of the steakhouse marinade for a less beefy flavor. Alternatively, try Head Country’s all-purpose marinade for a richer beef flavor.

Why does my steak bleed all over the place when I slice it?

First, it’s not bleeding… so let’s just get past that. The juices come out when you haven’t properly rested your steak. Resting allows the juices to redistribute through the meat making for better flavor, juiciness, and overall steak if you allow the meat to properly rest post cooking.

  • Let the steak rest for 10 minutes before cutting into it so the moisture can redistribute
  • Why is my steak tough?

    For the most tender bite, make sure to slice against the grain. This shortens the muscle fibers for a more tender texture.

    How to store

    Leftover sous vide flat iron steak can be wrapped tightly in foil and stored in the fridge for up to 3 days. To reheat, roll thin slices into a preheated skillet with oil or butter and place under the broiler for a minute or two.

    Close up of sliced flat iron - served medium rare after a sous vide cook for perfect pink slices over a bed of french fries.

    More Beef Recipes to Try

    Sous Vide Flat Iron Steak

    5 from 1 vote
    Prep: 6 hrs 10 mins
    Cook: 1 hr 15 mins
    Resting Time: 10 mins
    Servings: 8
    Sous Vide Flat Iron Steak sliced over frites
    This flat iron comes out perfect with a gentle sous vide cook before a finish on hot cast iron to lock-in that beef flavor and the kiss of Creole heat.

    Recommended Equipment

    • Vacuum Sealer
    • Food Safe Bag
    • Sous Vide Machine

    Ingredients  

    • 1 2-3 lbs flat iron steak
    • 1 cup Tony Chachere’s Pourable Steakhouse Marinade
    • 3 tbsp Tony Chachere’s Original Creole Seasoning
    • 2 tbs butter

    Instructions 

    Marinate the Steak:

    • Pour the marinade over the steak for 6 to 8 hours before cooking. Discard the marinade.

    Prep the Sous Vide:

    • Prep your sous vide machine according to the manufacturers’ directions for 125 degrees F.

    Prep the Flat Iron:

    • Pat the flat iron dry and rub with a liberal coating of 2 tbsp Tony Chachere’s Original Creole Seasoning all over.

    Sous Vide:

    • Place the flat iron in a food-safe bag and seal so there are no air pockets.
    • Submerge the now sealed steak in the water and set the timer for 1 hour.
    • When the flat iron has reached 125 degrees in the sous vide and is done, remove from the water and carefully remove the steak from the bag, reserving the juices.

    Sear:

    • Heat a cast-iron skillet over medium-high heat.
    • Add butter and swirl to coat the pan.
    • Sprinkle the remaining tablespoon of Tony Chachere’s seasoning over the steak and gently place into the pan. There will be a sizzle.
    • Sear on both sides until brown, 3 to 5 minutes, rotating and basting in butter as needed to form a good crust on all sides.
    • Use caution and an instant-read thermometer to not cook the steak past 135 degrees for rare.

    Serve:

    • Once the steak has rested a proper 10 minutes, slice in ⅛ to ¼” inch slices on a bias against the grain to serve.

    Video

    Notes

    • If you would like to cook the steak to medium or beyond, adjust the temperature of the sous vide to reflect your desired temp, minus 5 to 10 degrees. The final sear will finish the last 5 to 10 degrees of cooking for your steak to temp just where you want it.
    • Leftovers can be stored wrapped tightly in foil and in the fridge for up to 3 days.
    • Reheat by rolling thin slices in a preheated skillet with a touch of oil or butter. Or re-heat slices under the broiler for a minute or two.
    • If you don’t have Tony Chachere’s Steakhouse Marinade on hand, try their Italian dressing instead! Different flavors but both options are great!

    Nutrition

    Serving: 1g | Calories: 380kcal | Carbohydrates: 11g | Protein: 34g | Fat: 21g | Saturated Fat: 9g | Cholesterol: 120mg | Sodium: 710mg | Potassium: 580mg | Fiber: 1g | Sugar: 8g | Vitamin A: 869IU | Vitamin C: 1mg | Calcium: 13mg | Iron: 4mg
    Course: Main Course
    Cuisine: American
    Author: Kita Roberts
    Keyword: flat iron, sous vide flat iron

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