Pat cube steaks dry with paper towels.
In one bowl: whisk together buttermilk and egg.
In another bowl: mix flour, seasoned salt, pepper, paprika, garlic powder, and onion powder.
Dip steak into flour mix, then into the buttermilk/egg, then back into the flour mix again. Press the coating on well for that classic crispy crust.
Let coated steaks rest on a baking sheet for 10–15 minutes to help the breading stick better during air frying.
Preheat air fryer to 400°F for 3–5 minutes.
Spray the basket and both sides of the steak with cooking spray.
Air fry at 400°F for 10–12 minutes, flipping halfway through and spraying the other side.
They should be golden brown and reach an internal temp of 145°F–160°F depending on preference.
In a saucepan, melt butter. Whisk in flour to make a roux.
Slowly add milk while whisking constantly until thick and smooth.
Season with salt and plenty of black pepper.