Heat 2 tablespoons of olive oil in a small skillet over medium heat. Add 1 cup of breadcrumbs and toast, stirring frequently, until golden brown and crisp, about 3-5 minutes. Remove from heat and set aside.
In a large skillet, melt 4 tablespoons of unsalted butter over medium heat. Add minced garlic and 1 teaspoon red pepper flakes. Cook until fragrant but not browned, about 1-2 minutes.
Add shrimp in a single layer, seasoning with salt and pepper. Cook for 2-3 minutes on each side until pink and opaque. Be careful not to overcook.
Stir in lemon zest and juice of 1 lemon, along with 1/4 cup chopped fresh parsley. Toss to combine and let flavors meld for a minute or two.
Add cooked pasta directly to the skillet with shrimp and sauce. Toss everything together to coat pasta evenly in the buttery garlic sauce.
Divide pasta and shrimp among plates. Sprinkle toasted breadcrumbs generously over the top. Add grated Parmesan cheese if desired. Serve immediately.
