Prep the steak: Pat the steak cubes dry with paper towels.
Season all over with salt, pepper, smoked paprika, and onion powder. Let them sit at room temperature for 15 minutes while you start the potatoes.
Cook the potatoes: Heat 1 tablespoon olive oil and 1 tablespoon butter in a large heavy skillet (cast iron is best) over medium heat. Add the potatoes cut-side down with a pinch of salt and pepper.
Cook, stirring occasionally, until golden and tender, about 12–15 minutes. If they brown too fast, lower the heat. Transfer to a plate and tent loosely with foil.
Sear the steak bites: Increase heat to medium-high.
Add remaining 1 tablespoon olive oil. Work in batches to avoid crowding. Sear steak bites 1–2 minutes per side until browned with a pink center, about 4–5 minutes total per batch.
Transfer seared steak to a plate.
Make the garlic butter: Reduce heat to medium-low. Add remaining 2 tablespoons butter. Stir in minced garlic and crushed red pepper flakes.
Cook 30–45 seconds until fragrant. Do not brown the garlic.
Add BBQ flavor: Stir in BBQ sauce and Worcestershire. Let it bubble for 30 seconds to thicken slightly.
Taste and adjust with salt or pepper if needed.
Bring it together: Return potatoes to the skillet and toss to coat. Fold the steak bites back in, along with any juices from the plate. Warm through for 1–2 minutes, gently stirring so the crust stays intact.
Finish and garnish: Remove from heat.
Squeeze a little lemon over the top if using. Sprinkle with chopped parsley or chives. Serve hot, straight from the skillet.