
Season the steak. Pat the cubed steak dry with a paper towel, then season with salt, pepper, and red pepper flakes.
Sear the steak. Heat a large cast-iron pan over medium-high heat. Once the pan is hot, add the oil. After the oil starts shimmering, add the steak bites in a single layer. Sear for about 1 to 2 minutes on each side, until browned. Then remove the steak to a plate.
Make the garlic butter sauce. Reduce the heat to medium-low, then add the butter, shallot, and garlic, and saute for 1 minute.
Finish the steak bites. Add the steak bites back to the pan and stir with the garlic butter sauce to coat. Remove the pan from the heat and stir in the chopped parsley.