Place the split bagels cut-side-up in a 6-quart air fryer. Cook at 350 degrees F until lightly toasted, about 2 minutes (see Cook’s Note).
Remove the bagels from the air fryer. Top each with 2 tablespoons tomato sauce, 1 slice of provolone, ¼ cup shredded mozzarella, ¼ teaspoon oregano and ⅛ teaspoon crushed red pepper flakes if using. Add other optional toppings if using.
Return the bagels to the air fryer. Cook at 350 degrees F until the bagels are well toasted and the cheese is melted and starts to brown in spots, 4 to 5 minutes more. Sprinkle with Parmesan and serve immediately.
