Cook the Pasta: Bring a large pot of salted water to a boil. Add the spaghetti or bucatini and cook according to package instructions until al dente. Reserve 1 cup of pasta water, then drain the rest and set aside.
Prepare the Sauce: In a large skillet over medium heat, melt the butter. Add the minced garlic and red pepper flakes, sautéing until the garlic is fragrant but not browned, about 1-2 minutes.
Create a Creamy Base: Pour in the heavy cream and stir to combine. Allow the mixture to simmer gently for about 3-5 minutes until it thickens slightly.
Add Cheese and Flavor: Gradually whisk in the grated Parmesan cheese until melted and smooth. Stir in the lemon zest and lemon juice. Season the sauce with salt and black pepper to taste.
Combine Pasta and Sauce: Add the cooked pasta to the skillet with the sauce. If the sauce is too thick, gradually add reserved pasta water until the desired consistency is achieved. Toss everything together to coat the pasta evenly in the sauce.
Garnish and Serve: Once combined, remove from heat. Serve the pasta in bowls, garnished with freshly chopped parsley and, if desired, a sprinkle of crispy fried shallots for added texture.
Notes
Adjust the red pepper flakes to control the spice level.