Preheat the air fryer. Set it to 375°F (190°C) for 3–5 minutes.
A preheated basket helps the bread crisp right away.
Prep the bread. Spread a thin, even layer of butter or mayo on one side of each slice. That buttered side will face outward and get golden in the air fryer.
Build the base. Flip two slices so the unbuttered sides face up. Spread 1–2 tablespoons of pizza sauce on each.
Keep it thin to avoid sogginess.
Add cheese and toppings. Sprinkle a generous layer of mozzarella over the sauce. Add pepperoni and any extras. Top with a bit more mozzarella to “glue” the toppings in place.
Finish with a dash of Italian seasoning and a pinch of red pepper flakes if you like heat.
Cap the sandwich. Place the remaining bread slices on top, buttered side facing out. Press gently so everything sticks together.
Air fry, side one. Lightly spray the basket with oil or use a parchment liner with holes. Place sandwiches in a single layer.
Cook for 4–5 minutes at 375°F (190°C).
Flip and finish. Carefully flip with a spatula. Cook another 3–5 minutes until the bread is deep golden and the cheese is fully melted. Total time is usually 7–10 minutes, depending on your air fryer and bread thickness.
Optional cheesy crust. For extra flavor, sprinkle a teaspoon of Parmesan on the top of each sandwich during the last 1–2 minutes of cooking.
Rest and serve. Let sandwiches rest for 1 minute to set the cheese.
Slice in halves or triangles. Serve with warm pizza sauce for dipping.
Batch note. If making multiple, keep finished sandwiches on a wire rack in a 200°F (95°C) oven so the bottoms stay crisp.