Preheat your oven to 425°F (220°C) and line a baking sheet with parchment paper or lightly grease it.
If using store-bought pizza dough, let it come to room temperature for 20 minutes to make it easier to work with.
Lightly flour a clean surface and roll out the pizza dough into a large circle. If making individual calzones, divide the dough into 2 or 4 pieces and roll each into an 8-inch circle.
In a bowl, mix ricotta cheese, shredded mozzarella, Parmesan, garlic powder, Italian seasoning, salt, and black pepper.
Spread a thin layer of pizza sauce on half of each dough circle (optional).
Layer the pepperoni slices on top of the sauce, then spoon the cheese mixture over the pepperoni.
Fold the dough over the filling to form a half-moon shape. Press the edges together firmly and crimp with a fork or pinch with fingers to seal.
Brush the top with olive oil or egg wash for a golden crust.
Bake for 15-20 minutes, or until golden brown and crisp.
Let cool for a few minutes before slicing. Serve warm with extra pizza sauce for dipping.