Bring water to boil. Add salt. Cook pasta to al dente doneness. Drain pasta and make sure to keep at least 1/2 cup of the cooking liquid. Set aside the pasta to drain.
While the pasta cooks, prepare the sauce and shrimp. In a bowl, combine shrimp with olive oil and cajun seasoning. Mix well.
Large skillet on medium heat. Butter should be melted. Place shrimp in one layer. Cook until golden brown, turning once. To allow enough space, you may need to cook shrimp in two batches. After cooking is complete, transfer the shrimp to a plate.
Pour heavy cream into a pan. Scrape bottoms to loosen food stuck to the bottom. Allow cream to bubble. Turn heat down to low, and add parmesan cheese. Stir in cooked shrimp and pasta. To thin the sauce, add pasta water one tablespoon at time until you achieve the desired consistency.