Prep the steak: Pat the steak cubes dry with paper towels. This helps you get a great sear. Season all sides generously with salt and black pepper.

Preheat your pan: Set a large heavy skillet (cast iron works best) over medium-high heat. Add 1 tablespoon olive oil and 1 tablespoon butter. Let it get hot and shimmering.

Sear in batches: Add about half the steak cubes in a single layer with space between each piece. Don’t crowd the pan. Sear for 1–2 minutes per side until browned with a crust, about 3–4 minutes total. Transfer to a plate and repeat with the remaining steak, adding a little more oil if needed.

Build the garlic butter: Lower the heat to medium. Add the remaining butter to the pan. Stir in the minced garlic and cook for 30 seconds, just until fragrant—don’t let it brown.

Add the herbs: Stir in Italian seasoning, chopped rosemary, and a pinch of red pepper flakes. Let the herbs bloom in the butter for 15–20 seconds.

Return the steak: Add the seared steak bites and any juices back to the pan. Toss to coat in the garlic-herb butter for 1–2 minutes to warm through.

Brighten it up: Zest half the lemon over the pan and squeeze in about 1 tablespoon lemon juice. Toss again. Taste and adjust salt and pepper.

Finish and serve: Turn off the heat. Sprinkle with chopped parsley and, if using, a light shower of Parmesan. Serve immediately over zucchini noodles or cauliflower rice, or alongside a simple arugula salad.