Boil pasta according to package directions. Reserve ½ cup of the pasta water, then drain and set aside.
In a large skillet over medium-high heat, heat 1 tbsp olive oil. Season shrimp with 1 tsp Cajun seasoning and cook for 1–2 minutes per side until pink and opaque. Remove and set aside.
Add another drizzle of olive oil to the same pan. Sauté sliced bell peppers for 5–7 minutes until tender. Remove and set aside.
Reduce heat to medium. Add butter and minced garlic. Sauté for 1 minute until fragrant.
Pour in the heavy cream and reserved pasta water. Stir in paprika, chili flakes, onion powder, and 1 tsp Cajun seasoning. Let the sauce simmer for 4–5 minutes.
Stir in parmesan and mix until melted and the sauce is smooth and creamy.
Add the cooked pasta, bell peppers, and shrimp back into the pan. Toss until everything is well coated in the sauce.
Top with fresh or dried parsley and serve immediately.