Preheat the air fryer to 400°F (200°C).
Cut the sirloin steak into 1½-inch cubes.
Pat the steak dry with paper towels to help achieve a beautiful sear.
In a large bowl, whisk together the olive oil, melted butter, minced garlic, salt, and black pepper.
Add the steak cubes and toss until evenly coated.
Arrange the Air Fryer Steak Bites in a single layer inside the air fryer basket. Avoid overcrowding.
Cook for:
7–8 minutes for medium-rare
9–10 minutes for medium
11–12 minutes for medium-well
Flip the steak halfway through cooking for even browning.
Remove from the air fryer and let rest for 3 minutes before serving.