01 - Bring a large pot of salted water to a boil. Cook pasta until al dente according to package instructions. Reserve ½ cup pasta water, then drain pasta.
02 - Pat shrimp dry and season with kosher salt and black pepper.
03 - Heat olive oil in a large skillet over medium-high heat. Cook shrimp 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 aromatic.
05 - Add fresh baby spinach and cook, stirring, for about 1 minute until just wilted.
06 - Stir in lemon zest, lemon juice, and broth. Simmer for 1 minute, scraping up browned bits.
07 - Reduce heat to low and stir in unsalted butter until melted.
08 - Return drained pasta and cooked shrimp to the skillet. Toss to combine, adding reserved pasta water as needed for a silky texture.
09 - Stir in grated Parmesan cheese. Adjust seasoning with salt, pepper, or additional lemon juice to taste.
10 - Plate immediately, garnished with chopped fresh parsley, extra Parmesan, and lemon wedges.