Preheat your air fryer to 400°F (200°C).
In a mixing bowl, combine the melted butter, minced garlic, dried thyme, onion powder, paprika, salt, and pepper.
Add the steak cubes to the bowl and toss well to coat them in the garlic butter mixture. Let them marinate for 10 minutes.
In another bowl, toss the halved baby potatoes with a tablespoon of the garlic butter mixture, adding a pinch of salt and pepper.
Place the seasoned potatoes in the air fryer basket and cook for 10 minutes.
After 10 minutes, shake the basket and add the marinated steak bites to the potatoes in the air fryer.
Cook for an additional 8-10 minutes, shaking the basket halfway through, until the steak reaches your desired level of doneness (medium-rare is about 135°F or 57°C).
Once cooked, remove the basket from the air fryer and let the dish rest for a couple of minutes before serving.
Garnish with fresh parsley if desired.