Soy-Marinated Asian Flat Iron Steak

Combine soy sauce, vinegar, brown sugar, green onions, garlic, and mustard powder in a bowl to create the marinade. Pour this mixture into a resealable plastic bag, then add the steak and coat it evenly with the marinade. Remove any excess air from the bag before sealing it tightly. Refrigerate for 3 to 4 hours, allowing the steak to absorb the flavors.

Next, remove the steak from the marinade and discard any remaining liquid.

Heat a non-stick skillet over medium-high heat, allowing it to reach the optimal temperature for searing. Cook the steak just until the outside is nicely browned and crispy, about 1 minute per side. Continue cooking the steak until it reaches your desired level of doneness, approximately 5 minutes more per side. To ensure the steak is cooked to a safe temperature, insert an instant-read thermometer into the center of the meat and check that it reaches 140 degrees F (60 degrees C).

Once cooked, remove the skillet from heat and allow the steak to rest for 3 to 5 minutes. During this time, it will retain its juices and become more tender. Finally, sprinkle sesame seeds over the steak to add a burst of flavor and texture.