Bring a large pot of salted water to a boil. Add the fettuccine and cook according to package instructions until al dente. Once cooked, reserve about 1 cup of pasta water and then drain the fettuccine in a colander.
In a large skillet, melt the 6 tablespoons of unsalted butter over medium heat. Once melted, add the finely minced onion (or onion powder) and sauté for about 2-3 minutes until translucent. Then, add the minced garlic and Italian seasoning, cooking for an additional minute until fragrant.
Pour in the heavy cream, stirring to combine. Allow the mixture to simmer gently for about 3-4 minutes, letting it thicken slightly. Gradually whisk in the freshly grated Parmesan cheese until melted and smooth. If the sauce is too thick, add a bit of the reserved pasta water until you reach your desired consistency.
Add the drained fettuccine to the skillet with the creamy sauce, tossing to coat the pasta evenly. Season with salt and pepper to taste. If needed, add more reserved pasta water to loosen the sauce.
Once everything is well combined, serve the fettuccine alfredo immediately, garnished with fresh parsley if desired. Enjoy every creamy, cheesy bite!
