Fill a large pot with 4 quarts of water, then stir in 1 tablespoon of salt and bring it to a boil. Once boiling, add the fettuccine and cook until it reaches al dente. Drain the pasta and set it aside.
In a large skillet, warm the Alfredo sauce over low heat. Stir in the drained tuna, and add a pinch of salt and pepper.
Once the sauce is heated through, toss in the cooked pasta until evenly coated.
Adjust seasonings as needed. Serve warm, garnished with fresh parsley and grated Parmesan.