Bring a large pot of salted water to a rolling boil. Add fettuccine and cook according to package directions until al dente, usually 9-11 minutes. Before draining, reserve 1/4 cup of the starchy pasta water, then drain and set aside.

While pasta cooks, pat salmon fillets completely dry with paper towels. Season both sides generously with salt and pepper.

Heat olive oil in a large skillet over medium-high heat until it shimmers. Carefully place salmon fillets in pan and cook for 3-4 minutes without moving them until edges turn opaque halfway up the fillet.

Flip salmon carefully and cook for another 3-4 minutes until fish is cooked through, flakes easily with a fork, and reaches 145°F internal temperature. Transfer to a plate and gently flake into bite-sized pieces.

In same skillet over medium heat, add minced garlic and sauté for about 30 seconds until fragrant but not browned. Pour in heavy cream and bring to a gentle simmer. Cook for 2-3 minutes, stirring occasionally, until it thickens slightly and coats the back of a spoon.

Stir in lemon juice and grated parmesan cheese, whisking until cheese melts completely into sauce. Season with salt and pepper to taste. If sauce seems too thick, add reserved pasta water to reach desired consistency.

Add cooked fettuccine and flaked salmon to skillet, tossing gently to coat everything in creamy sauce. Cook for 1 minute to heat through, then remove from heat and sprinkle with fresh dill or parsley before serving.