Bring a large pot of salted water to a boil. Add the fettuccine pasta and cook according to the package instructions until al dente. Reserve about ½ cup of pasta water, then drain and set the pasta aside.
Heat 1 tablespoon of olive oil in a large skillet over medium heat. Add the sliced turkey sausage and cook until browned and cooked through, about 5 minutes. Remove the sausage from the pan and set it aside.
In the same skillet, add the remaining tablespoon of olive oil. Toss the shrimp with Cajun seasoning, salt, and pepper. Add the shrimp to the skillet and cook for 2-3 minutes per side until they turn pink and opaque. Remove shrimp and set aside with the sausage.
To the skillet, add diced onion, bell pepper, and minced garlic. Cook over medium heat until softened and fragrant, about 4-5 minutes.
Stir in the diced tomatoes and cook for another 2 minutes. Pour in the heavy cream, stirring to combine. Allow the sauce to simmer gently for 3-4 minutes until it thickens slightly.
Return the cooked sausage and shrimp to the skillet. Toss in the cooked fettuccine and use reserved pasta water a little at a time to loosen the sauce if needed. Stir everything together until evenly coated and heated through. Adjust seasoning with salt, pepper, and extra Cajun seasoning if desired.
Sprinkle chopped parsley over the top for a fresh, vibrant finish. Serve immediately and enjoy the perfect harmony of spicy, creamy, and savory flavors.