01 - Bring a large pot of salted water to a boil. Cook pasta according to package instructions until al dente. Reserve ½ cup pasta water, then drain pasta.
02 - Pat shrimp dry and season with salt and pepper.
03 - Heat olive oil in a large skillet over medium-high heat. Add shrimp and cook 1 to 2 minutes per side until opaque and lightly golden. Transfer shrimp to a plate.
04 - In the same skillet, add minced garlic and crushed red pepper flakes if using. Sauté for 30 seconds until fragrant.
05 - Add fresh spinach and cook, stirring, until just wilted, about 1 minute.
06 - Stir in lemon zest, lemon juice, and broth. Simmer for 1 minute, scraping up any browned bits.
07 - Reduce heat to low, add unsalted butter, and stir until melted.
08 - Add drained pasta and cooked shrimp to the skillet. Toss to combine, adding reserved pasta water as needed to achieve a silky sauce.
09 - Stir in Parmesan cheese. Adjust seasoning with salt, pepper, or additional lemon juice to taste.
10 - Plate immediately and garnish with chopped parsley, extra Parmesan cheese, and lemon wedges.