Cook the pasta according to package instructions.
While the pasta is cooking, season the shrimp with the cajun seasoning. In a large skillet heat 1 tbsp of the olive oil over medium high heat. Add the shrimp and cook on both sides until pink, it shouldn't take more than a couple minutes. Remove the shrimp from the skillet and set aside.
Add the remaining 1 tbsp of olive oil and the butter to the skillet and heat until butter melts over medium heat. Add the chopped onion and garlic, then cook for about 3 minutes until the onion becomes soft and translucent.
While the onion is cooking pour the tomatoes in a food processor or blender and pulse until smooth. Add the tomatoes to the skillet, bring to a boil then turn down the heat and simmer for about 15 minutes, stirring occasionally.
Add the heavy cream and Parmesan cheese to the skillet, and cook for another 5 minutes. Taste and season with salt and pepper as needed.
Add the cooked pasta and shrimp to the skillet and toss everything well together.
Garnish with fresh basil and more Parmesan cheese if preferred, and serve immediately.