01 - Bring a large pot of salted water to a boil. Cook the spaghetti according to package directions until al dente. Reserve ½ cup of pasta water and drain the pasta.
02 - While the pasta cooks, pat the shrimp dry and season with salt and black pepper.
03 - Heat olive oil in a large skillet over medium-high heat. Add the shrimp in a single layer and cook 1-2 minutes per side until pink and opaque. Remove shrimp and set aside.
04 - In the same skillet, add minced garlic and red pepper flakes, if using. Sauté for 30 seconds until fragrant without browning.
05 - Pour in dry white wine or chicken broth and scrape up browned bits from the skillet. Simmer for 2-3 minutes to reduce slightly.
06 - Stir in lemon zest, lemon juice, and fresh spinach. Toss until the spinach wilts, about 1 minute.
07 - Return shrimp to the skillet. Add drained pasta, butter, and Parmesan cheese. Toss to combine, adding reserved pasta water as needed to achieve a silky sauce consistency.
08 - Remove from heat. Stir in chopped parsley and adjust seasoning with additional lemon juice, salt, or black pepper as preferred.
09 - Plate immediately with extra Parmesan and a drizzle of olive oil if desired.