Heat a large skillet over medium-high heat.
Season steak cubes with salt and black pepper.
Add 1 tablespoon butter to the skillet.
Sear steak bites for 2–3 minutes per side until browned.
Remove steak from the skillet and set aside.
In the same skillet melt the remaining butter.
Add garlic, lemon juice, Dijon mustard, paprika, and red pepper flakes.
Stir and cook for about 1 minute until fragrant.
Return steak bites to the skillet and toss in the cowboy butter sauce.
Sprinkle chopped parsley on top and serve immediately.