Preheat the air fryer to 355 degrees F (180 degrees C).

Combine sirloin, 2 tablespoons tomato sauce, onion, oats, Italian seasoning, parsley, salt, and pepper in a bowl and mix until just incorporated. Form into 2 small loaves that are approximately 4 1/2 inches long and 2 inches wide.

Lightly spray the inner basket of the air fryer with cooking spray. Add the 2 loaves, without touching one another, and lightly brush the tops with the remaining 1 tablespoon tomato sauce.

Air-fry meatloaves until an instant-read thermometer inserted into the center reads 165 degrees F (73 degrees C), 17 to 20 minutes.