Grab your sirloin and slice it into even, bite-sized chunks. About 1-inch cubes work perfectly. Try to cut them all roughly the same size so they cook evenly no one wants some pieces dry while others are still mooing.
In a medium bowl, whisk together the olive oil, salt, pepper, onion powder, garlic powder, and brown sugar. It’s a simple mix, but trust me, that brown sugar makes a difference it helps caramelize the outside just enough for that delicious, golden crust.
Toss your steak bites into the bowl and mix until every piece is coated in that flavorful goodness. Let them sit for 15–20 minutes if you’ve got the time. (No stress if you’re in a hurry just give them a few minutes while your air fryer heats up.)
Set your air fryer to 400°F (200°C). Let it get nice and hot while your steak is soaking in all that flavor.
Pop the marinated steak pieces into the air fryer basket in a single layer. Don’t crowd them give them space to breathe! Depending on your air fryer size, you may need to do two batches.
Cook at 400°F for 4–6 minutes, flipping halfway through. Less time for medium-rare, a little more for medium-well. These cook fast, so keep an eye on them.
While the steak is cooking, melt your butter in the microwave (or on the stove if you’re feeling fancy). Stir in the minced garlic and parsley. That’s it. The smell alone might make you drool.
Once your steak bites are beautifully browned and cooked to your liking, transfer them to a plate or bowl and drizzle that luscious garlic butter right over the top. Toss gently to coat.
Let them rest for a minute or two just enough time for the butter to sink into every nook and cranny and the juices to settle.