01 - Bring a large pot of salted water to a boil. Cook the pasta according to package instructions until al dente. Reserve 1/4 cup of pasta water, then drain and set aside.
02 - While pasta cooks, pat shrimp dry and season with salt and pepper.
03 - In a large skillet over medium heat, heat 1.5 tablespoons olive oil and 1 tablespoon butter. Add shrimp in a single layer and cook 1–2 minutes per side, until just opaque. Remove shrimp to a plate.
04 - In the same skillet, add remaining olive oil and butter. Add garlic and red pepper flakes; sauté 30 seconds until fragrant.
05 - Add spinach and cook, stirring, until wilted (about 1–2 minutes).
06 - Return shrimp to skillet. Add lemon zest and juice. Toss to combine.
07 - Add drained pasta and reserved pasta water. Toss everything together until the sauce lightly coats the pasta.
08 - Taste and adjust seasoning with more salt, pepper, or lemon as desired. Serve immediately, topped with fresh parsley if using.