Arrange the shrimp in a single layer on a large, rimmed, broiler-safe baking sheet.
Pour the melted butter or olive oil on the shrimp and toss to coat.
Sprinkle the shrimp with kosher salt, black pepper, garlic powder, crushed red pepper, and grated parmesan.
Bake until the shrimp are pink and opaque, about 8 minutes. If you want the parmesan to brown, finish by broiling them for about 1 minute.
Transfer the shrimp to a serving platter and spoon the pan juices over them. Serve immediately.
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Notes
Need to defrost your shrimp? Fill a large bowl with cool water. Add the shrimp. Replace the water once or twice, gently separating frozen shrimp that have stuck to each other. They should be fully defrosted in about 10 minutes. Drain them using a colander, then dry them on paper towels.
If your shrimp are very cold (this can happen if you just defrosted them), the melted butter will harden when it touches them. In this case, it's better to use olive oil.
You can keep the leftovers in the fridge in a shallow, airtight container for up to three days. Reheat them gently, covered, in the microwave at 50% power. Or serve them cold with cocktail sauce or sriracha mayo for dipping. They are also excellent when served cold in a salad.