Begin by cutting your sirloin or ribeye into 1-inch cubes and patting them dry. Season generously with salt and black pepper, then let sit at room temperature for 15 minutes.

Preheat a cast-iron skillet over medium-high heat for about 3 minutes. Add olive oil once hot until shimmering.

Carefully place the steak cubes in the skillet in a single layer. Sear for about 2 minutes on each side until browned. Remove and let rest.

Reduce heat to medium, add butter to the skillet. Once melted, stir in garlic and cook for about 30 seconds until fragrant.

Return steak bites to the skillet, tossing gently in garlic butter mixture. Cook for an additional minute, then garnish with parsley and red pepper flakes before serving.