Bring a large pot of salted water to a rolling boil. Add fettuccine pasta and cook according to package directions for 8-10 minutes. Reserve half a cup of pasta water, then drain.

In a large skillet over medium heat, melt 4 tablespoons of butter. Whisk in 2 tablespoons of all-purpose flour and cook for about 1 minute.

Gradually pour in 2 cups of whole milk while whisking. Stir until the mixture is smooth for about 2-3 minutes.

Add 4 ounces of cream cheese to the skillet, stirring until fully melted and combined, around 2-3 minutes.

Mix in ¾ cup of freshly grated Parmesan cheese, ½ teaspoon of garlic powder, and ½ teaspoon of onion powder. Season with salt and pepper.

Gently fold in 8 ounces of lump crabmeat, allowing it to heat through for about 2-3 minutes.

Carefully add the cooked fettuccine to the skillet, tossing to coat with the sauce. Adjust thickness with reserved pasta water as needed.

Serve immediately, garnished with 2 tablespoons of chopped fresh parsley.