Preheat your air fryer to 400 degrees Fahrenheit.
Peel the sweet potato and cut into small half-inch cubes to ensure even cooking.
Trim any excess fat from the sirloin steak and cut into one-inch bite-sized pieces.
In a mixing bowl, toss the sweet potato cubes with the olive oil and half of the garlic powder, smoked paprika, sea salt, and black pepper.
Place the seasoned sweet potatoes in the air fryer basket in a single layer and cook for 10 minutes, shaking halfway through.
While potatoes cook, toss the steak cubes, diced red bell pepper, and red onion with the remaining spices.
Add the steak and pepper mixture to the air fryer basket with the sweet potatoes.
Air fry for an additional 5 to 7 minutes, or until the steak reaches your desired level of doneness and the potatoes are tender and golden.
Remove from the air fryer and let the steak rest for 2 minutes before serving.