Begin by bringing a large pot of salted water to a boil. Add the fettuccine and cook according to the package instructions until al dente, usually about 8-10 minutes. Reserve about 1 cup of the pasta cooking water, then drain the fettuccine and set it aside.
In a large skillet, melt 2 tablespoons of butter over medium heat. Once melted, add the prewashed baby spinach. Sauté for 2-3 minutes, or until the spinach is wilted. Remove the spinach from the skillet and set it aside.
In the same skillet, add the remaining 2 tablespoons of butter. Once melted, pour in the heavy cream and bring it to a gentle simmer. Stir occasionally, letting it cook for about 3-4 minutes until it thickens slightly.
Gradually whisk in ¾ cup of the grated Parmesan cheese, stirring until melted and smooth. Season the sauce with salt, freshly ground pepper, and a pinch of freshly grated nutmeg for that extra depth of flavor.
Add the cooked fettuccine to the skillet along with the sautéed spinach. Toss everything together until the pasta is well coated with the creamy sauce. If the sauce is too thick, add a splash of the reserved pasta water to achieve your desired consistency.
Serve your Spinach Alfredo Pasta immediately, garnished with the remaining Parmesan cheese and a sprinkle of freshly ground pepper. Enjoy this creamy, comforting dish with your favorite side salad or garlic bread for a complete meal.