Bring a large pot of salted water to a rolling boil. Cook fettuccine according to package directions until al dente, usually 9 to 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. Place salmon fillets in the pan and cook for 3 to 4 minutes without moving them until edges turn opaque halfway up the fillet.

Flip salmon carefully and cook another 3 to 4 minutes until the fish reaches an internal temperature of 145°F and flakes easily with a fork. Transfer to a plate and gently break into bite-sized pieces.

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

Stir in lemon juice and grated parmesan, whisking until fully melted into the sauce. Season with salt and pepper to taste. Add a splash of reserved pasta water if the sauce feels too thick.

Add the cooked fettuccine and flaked salmon to the skillet. Toss gently to coat everything in the creamy sauce, cook for 1 minute to heat through, then top with fresh dill or parsley and serve right away.