Preheat oven: Set your oven to 425°F (220°C). Place the oven rack in the center position and line a baking sheet with parchment paper or lightly greased foil.
Prep the squash: Wash and dry the squash. Slice into ¼-inch thick rounds.
Arrange and season: Lay the squash slices in a single layer on the prepared baking sheet. Sprinkle lightly with garlic salt and black pepper.
Add Parmesan: Spoon a thin, even layer of Parmesan onto each squash slice, covering the tops.
Bake: Place in the oven for 15–20 minutes, or until the cheese is melted, golden brown, and slightly crispy. Watch closely near the end—remove earlier if the cheese browns too fast.
Optional crisping: For extra crunch, broil on high for 1–2 minutes before serving.
Serve hot: Enjoy immediately, straight from the oven, for the best flavor and texture.