01 - Pat steak cubes dry with paper towels. Season evenly with salt and black pepper.
02 - Heat olive oil in a large skillet over high heat.
03 - Add steak cubes in a single layer. Sear for 2-3 minutes without moving, then flip and cook for another 2-3 minutes until browned. Cook in batches if necessary to avoid overcrowding.
04 - Reduce heat to medium-low. Add butter and minced garlic to the pan. Stir continuously for 1-2 minutes until butter melts and garlic becomes fragrant, coating the steak cubes.
05 - Sprinkle chopped parsley and red pepper flakes, if using. Toss to combine and serve immediately.