01 - Pat steak cubes dry with paper towels and season all sides evenly with kosher salt and freshly ground black pepper.
02 - Place a large heavy skillet over high heat and add olive oil. Heat until shimmering.
03 - Add steak cubes in a single layer without overcrowding. Sear undisturbed for 1 to 2 minutes until a brown crust forms.
04 - Turn steak cubes and cook an additional 1 to 2 minutes until medium-rare or desired doneness is reached. Transfer steak bites to a plate and set aside.
05 - Reduce heat to medium-low, add butter to the pan, and once melted, stir in minced garlic. Sauté for 30 seconds until fragrant.
06 - Return steak cubes to the skillet, tossing to coat with garlic butter. Sprinkle with fresh parsley and, if desired, crushed red pepper flakes.
07 - Serve immediately, optionally garnished with a squeeze of lemon juice or grated Parmesan.