Bring a large pot of salted water to a boil over high heat. Add the fettuccine pasta and cook for 10-12 minutes until al dente, stirring occasionally. Once cooked, drain the pasta in a colander, reserving a cup of pasta water for later use. Set the pasta aside and keep it warm.

In a large skillet, melt 4 tablespoons of butter over medium heat until it starts to bubble. Add 3 minced garlic cloves and sauté for 1-2 minutes until fragrant. Pour in 1 cup of heavy cream and let it simmer gently for 15-20 minutes, stirring occasionally, until the sauce thickens.

Reduce the heat to low and gradually add 1 cup of freshly grated Parmesan cheese, stirring continuously until melted and blended into the creamy mixture.

Gently fold in 8 ounces of crab meat into the sauce, stirring gently. Cook for 2-3 minutes to warm the crab.

Add the cooked fettuccine pasta to the crab Alfredo sauce. Toss the pasta for 2-3 minutes, ensuring it's well coated with the sauce.

Transfer the dish to serving plates. Garnish with freshly chopped herbs or lemon zest and serve hot.