Bring a large pot of salted water to a boil. Add the linguine and cook according to package instructions until al dente. Drain and set aside, reserving 1/2 cup of pasta water.
Season the shrimp with garlic powder, onion powder, paprika, and 1 tablespoon of Cajun seasoning. In a skillet, melt 1 tablespoon of butter over medium heat. Cook the shrimp for 2-3 minutes per side until pink and opaque. Remove and set aside.
In the same skillet, add sliced smoked sausage and cook for 1-2 minutes per side until browned. Remove and set aside.
Add diced green bell pepper, onion, mushrooms, and minced garlic to the skillet. Sauté for 3-4 minutes until vegetables are tender.
Add crushed tomatoes, heavy cream, lemon juice, and remaining Cajun seasoning to the skillet. Stir well and bring to a simmer. Let it cook for 10-12 minutes until the sauce thickens.
Add the cooked linguine to the skillet, tossing to coat the pasta in the sauce. If the sauce is too thick, add reserved pasta water a little at a time until desired consistency is reached.
Return the cooked shrimp and sausage to the skillet, stirring gently to combine. Serve hot, garnished with chopped parsley and grated Parmesan cheese, if desired.