Prep the fresh shell-on shrimp by rinsing under cold water, removing shells and deveining, then patting dry with paper towels.

In a mixing bowl, combine melted butter, minced garlic, and grated Parmesan cheese with black pepper and red pepper flakes until smooth.

Add prepared shrimp to the marinade and thoroughly coat each piece.

Preheat the oven to 400°F (200°C) for baking.

Line a baking tray with parchment, spread shrimp in a single layer, and bake for 10-12 minutes.

Remove from oven, let rest for a minute, and serve immediately, garnished with parsley or lemon if desired.