Stepwise Method:

• Begin by bringing a large pot of salted water to a boil. Add the 6 ounces of fettuccine or linguine and cook according to package instructions until al dente. Reserve 1/2 cup of the pasta cooking water, then drain the pasta and set it aside.
• In a large skillet over medium heat, melt 3 tablespoons of unsalted butter. Add the minced onion and sauté for about 3-4 minutes, or until translucent. Add 2 teaspoons of minced garlic and cook for an additional minute, until fragrant.
• Pour in 1 cup of chicken broth and bring to a simmer. Reduce the heat to low and stir in 3/4 cup of heavy cream, 1/3 cup of freshly grated Parmesan cheese, 1/4 teaspoon of ground mustard, 1/4 teaspoon of onion powder, and 1/4 teaspoon of garlic powder. Stir until the cheese is melted and the sauce is smooth.
• Gently fold in the drained tuna and 3/4 cup of frozen peas. If you're using Dijon mustard, add it here for an extra layer of flavor. Season with salt and pepper to taste. Allow the mixture to heat through for about 3-5 minutes.
• Add the cooked pasta to the skillet with the creamy sauce. Toss to combine, adding reserved pasta water a little at a time if the sauce seems too thick. The pasta should be well coated in the creamy sauce.
• Serve the Creamy Tuna Pasta hot, garnished with freshly chopped flat-leaf parsley and a squeeze of lemon if desired. Enjoy your comforting bowl of deliciousness!