Boil the pasta: Bring a large pot of salted water to a boil. Cook pasta until just al dente.
Before draining, reserve 1 cup of the starchy pasta water. Drain and set aside.
Season the shrimp: Pat shrimp dry with paper towels. Season with 1/2 teaspoon salt, 1/4 teaspoon black pepper, and a pinch of red pepper flakes.
Sauté the shrimp: In a large skillet, heat 1 tablespoon olive oil and 1 tablespoon butter over medium-high heat.
Add shrimp in a single layer and cook 1–2 minutes per side until pink and just opaque. Transfer to a plate.
Build the sauce: Reduce heat to medium. Add remaining olive oil and 1 tablespoon butter to the same skillet.
Stir in garlic and a pinch of red pepper flakes. Cook 30–45 seconds until fragrant, not browned.
Deglaze: Pour in the wine (or broth), scraping up any browned bits. Simmer 1–2 minutes to reduce slightly.
Add lemon: Stir in lemon zest and 2 tablespoons lemon juice.
Taste and adjust with more juice for brightness.
Toss the pasta: Add drained pasta to the skillet with 1/3–1/2 cup reserved pasta water. Toss over medium heat until glossy and lightly saucy, 1–2 minutes. Add more pasta water as needed.
Finish: Return shrimp to the pan with remaining 1 tablespoon butter, parsley, and Parmesan (if using).
Toss until the butter melts and everything is well coated. Season to taste with salt, pepper, and extra lemon juice.
Serve: Plate immediately. Top with more parsley, Parmesan, and a squeeze of lemon.