Bring a large pot of salted water to a boil and cook fettuccine according to package directions until al dente.
Pat salmon cubes and shrimp dry with paper towels and season with salt and pepper.
In a large skillet over medium-high heat, add olive oil and sear salmon cubes for 2-3 minutes per side until golden and cooked through; remove from skillet and set aside.
In the same skillet, sear shrimp for 1-2 minutes per side until pink and opaque; remove and set aside with the salmon.
Reduce heat to medium, melt butter in the skillet, and sauté minced garlic for 60 seconds until fragrant.
Pour in heavy cream and bring to a gentle simmer for 3-5 minutes until the liquid reduces slightly.
Whisk in Parmesan cheese, oregano, and red pepper flakes, stirring continuously until the sauce is smooth and thickened.
Incorporate the cooked fettuccine into the sauce, tossing to coat thoroughly.
Gently fold the seared salmon and shrimp back into the pasta.
Garnish with chopped parsley and serve immediately.