Preheat the grill. Heat a gas or charcoal grill to medium-high. If using a grill pan or cast-iron skillet on the grill, set it on the grates while preheating so it gets blazing hot.
Pat the steak dry. Use paper towels to remove surface moisture.
Dry steak browns better and faster.
Season. In a bowl, toss the steak cubes with salt, pepper, smoked paprika, and olive oil until evenly coated.
Make the garlic butter. In a small heatproof pan, melt the butter over low heat (on a side burner or the cooler side of the grill). Add minced garlic and cook 30–60 seconds until fragrant, not browned. Stir in parsley and lemon juice.
Keep warm.
Grill the steak bites. Arrange steak in a single layer on the hot grates or grill pan. Don’t crowd. Cook 1.5–2 minutes per side, turning with tongs, until nicely seared.
Aim for medium-rare to medium for best tenderness.
Toss in garlic butter. Transfer steak bites to a bowl and immediately pour over the warm garlic butter. Toss to coat. Rest 2–3 minutes.
Finish and serve. Sprinkle with flaky salt if using.
Serve with toothpicks, over rice, or alongside roasted potatoes and greens.