Bring a large pot of salted water to a rolling boil over high heat. Add fettuccine and cook until al dente, about 8-10 minutes. Reserve 1/2 cup of the pasta water, then drain and set aside.

Pat the shrimp dry and season with Cajun seasoning. In a skillet, melt 2 tablespoons of butter over medium-high heat, add shrimp, and sear for 1-2 minutes until pink. Set aside.

In the same skillet, add another tablespoon of butter and sliced sausage. Cook until browned, then add diced onion, green, and red peppers. Sauté until softened, about 4-5 minutes. Add minced garlic and cook for 30 seconds.

Stir in halved cherry tomatoes and cook for another 3-4 minutes, allowing them to soften and release juices.

Pour in heavy cream and bring to a gentle simmer. Cook for 2-3 minutes until thickened. Add Gruyère cheese and smoked paprika, stirring until smooth.

Add reserved fettuccine and seared shrimp to the skillet. Toss gently, adding reserved pasta water to achieve your desired consistency.

Remove from heat, season with additional Cajun seasoning, and toss with chopped parsley. Serve hot.