Begin by bringing a large pot of salted water to a boil. Add the linguine and cook according to package instructions until al dente. Drain the pasta, reserving about 1 cup of the pasta water for later use.
In a large skillet, heat the olive oil and 2 tablespoons of butter over medium heat. Once the butter has melted, add the minced garlic and red pepper flakes. Sauté for about 1 minute until fragrant, being careful not to burn the garlic.
Add the large shrimp to the skillet and season with salt, pepper, and Italian seasoning. Cook for 2-3 minutes on each side until the shrimp are pink and opaque. Remove the shrimp from the skillet and set aside.
In the same skillet, add the remaining 4 tablespoons of butter along with the baby spinach. Sauté until the spinach is wilted. Pour in the reserved pasta water and lemon juice, and stir to combine, allowing the flavors to meld.
Add the drained linguine to the skillet, tossing to coat the pasta in the sauce. Return the shrimp to the skillet, and sprinkle in the Parmesan cheese. Stir everything together until well combined and the cheese has melted.
Divide the Lemon Garlic Parmesan Shrimp Pasta among serving plates. Garnish with chopped parsley and additional Parmesan cheese if desired. Enjoy immediately while hot!