Bring a large pot of water to a boil. Add salt and pasta. Cook pasta al dente. Drain pasta, reserving at least ½ cup of the pasta water, and set aside.
In a medium bowl, combine shrimp with cajun seasoning and olive oil.
Heat a large skillet to medium high heat. Melt butter, then add shrimp in a single layer.
Cook until golden brown on each side, turning only once. You may have to cook shrimp in two batches to allow enough room. Once finished cooking, transfer cooked shrimp to a clean plate and reduce heat to medium low.
Add heavy cream to skillet and scrape bottom to release any bits stuck. Allow cream to bubble. Reduce heat to low and stir in parmesan cheese to melt.
Add cooked pasta and shrimp, then stir gently to coat. Use reserved pasta water to thin out the sauce if needed.