Step 1

Prepare the following, adding each to a zip-top gallon bag as you complete it: Pick the leaves from 2 fresh rosemary sprigs until you have 2 teaspoons and coarsely chop, smash and peel 2 garlic cloves, trim and cut 2 medium scallions into 1-inch lengths.

Step 2

Add 2 tablespoons olive oil, 1 tablespoon balsamic vinegar, 1 tablespoon soy sauce, 1 teaspoon Dijon mustard, 3/4 teaspoon kosher salt, 1/2 teaspoon black pepper, 1/2 teaspoon smoked paprika, and 1/2 teaspoon ground coriander, and stir to combine. Add 1 flat iron steak, press to remove any air, and seal the bag. Massage the steak to coat in the marinade. Place on a plate and refrigerate for at least 4 hours and up to overnight.

Step 3

Remove the steak from the marinade and pat dry with paper towels. Heat 2 tablespoons neutral cooking oil in a large skillet over medium-high heat until shimmering. Add the steak and cook, rotating the pan 90° halfway through, until a golden-brown crust forms on the bottom, 4 to 5 minutes total. Flip the steak and repeat browning the second side.

Step 4

Reduce the heat to medium. Flip the steak and continue to cook, flipping every 1 to 2 minutes, until the thickest part of the steak registers 125°F to 130°F for medium rare, 4 to 6 minutes more (for a total cooking time of 12 to 15 minutes from when the steak first went into the pan). Transfer the steak to a clean cutting board and let rest for 5 minutes. Slice across the grain to serve.