01 - Bring a large pot of salted water to a boil. Add pasta and cook until al dente according to package directions. Reserve 1/2 cup pasta water, drain pasta, and set aside.
02 - Pat shrimp dry and season evenly with salt, black pepper, and red pepper flakes if using.
03 - Heat 2 tablespoons butter and 2 tablespoons olive oil in a large skillet over medium-high heat. Add shrimp in a single layer and cook 2 minutes per side until just opaque. Remove shrimp from skillet.
04 - To the same skillet, add remaining 2 tablespoons butter. Stir in minced garlic and sauté for 1 minute until fragrant but not browned.
05 - Add lemon zest and juice to the skillet. Return shrimp to the pan and toss to coat thoroughly.
06 - Add cooked pasta and reserved pasta water to skillet. Toss to combine, adding more pasta water if necessary to achieve a silky consistency.
07 - Stir in chopped parsley and Parmesan cheese. Adjust seasoning to taste.
08 - Plate immediately, garnished with additional parsley and Parmesan as desired.