Pat the shrimp dry with paper towels and season with salt, black pepper, and red pepper flakes. Set aside.
Bring a large pot of salted water to a boil and cook pasta until al dente. Reserve 1 cup pasta water, then drain.
Heat olive oil in a wide pan over medium-high heat. Add shrimp in a single layer.
Cook shrimp for 1–2 minutes per side until pink and firm. Remove and set aside.
Lower heat to medium. Add butter to the same pan and let it melt.
Add garlic and cook for about 20 seconds until fragrant.
Stir in lemon zest and white wine or pasta water to loosen the pan.
Add cooked pasta directly to the sauce and toss well.
Return shrimp to the pan and pour in lemon juice.
Add reserved pasta water as needed and toss until glossy.
Taste and adjust seasoning.
Finish with parsley and parmesan if using. Serve immediately.