Bring a large pot of salted water to a boil. Cook linguine pasta according to package instructions until al dente. Drain and set aside.
In a medium bowl, toss the shrimp with Cajun seasoning until evenly coated.
Heat olive oil in a large skillet over medium-high heat. Add the shrimp and cook for 2-3 minutes per side until pink and opaque. Remove shrimp from skillet and set aside.
Reduce heat to medium and add butter to the same skillet. Once melted, add minced garlic and chopped onion. Sauté for 2-3 minutes until fragrant and onion is translucent.
Pour in the dry white cooking broth, scraping the bottom of the skillet to loosen any browned bits. Simmer for 2 minutes to reduce slightly.
Stir in the heavy cream, Parmesan cheese, lemon juice, and crushed red pepper flakes. Cook for 3-4 minutes, stirring frequently, until the sauce thickens slightly.
Season the sauce with salt and freshly ground black pepper to taste.
Return the cooked shrimp to the skillet and toss to coat in the creamy Cajun sauce. Cook for an additional 1-2 minutes to heat through.
Add the cooked linguine to the skillet and toss everything together until the pasta is evenly coated with the sauce.
Remove from heat and sprinkle chopped fresh parsley over the top before serving.