Prep the steak: Pat the steak cubes dry with paper towels to remove surface moisture. Dry steak browns better. Season generously with salt, pepper, and paprika if using.

Heat the pan: Place a large heavy skillet (cast iron is ideal) over medium-high heat. Add the oil and let it get hot until shimmering.

Sear in batches: Add about half the steak bites in a single layer. Don’t crowd the pan. Let them sear undisturbed for 1–2 minutes to develop a crust, then flip and cook another 1–2 minutes. Transfer to a plate. Repeat with the remaining steak.

Lower heat and make garlic butter: Reduce heat to medium-low. Add the butter to the pan. When melted, add the minced garlic and red pepper flakes if using. Stir for 20–30 seconds until fragrant. Don’t let the garlic brown.

Coat the steak: Return the steak bites and their juices to the pan. Toss to coat in the garlic butter for about 30–60 seconds. Taste and adjust seasoning.

Finish and serve: Turn off the heat. Sprinkle with chopped parsley and a small squeeze of lemon for brightness. Serve immediately.