Season shrimp with 1 tablespoon of cajun seasoning and 1 tablespoon of olive oil. Let sit for 15 minutes.
Add 2 tablespoon of olive oil to a large saucepan on medium heat. Place shrimp evenly across the saucepan, you may have to do this in batches. Saute for 1-2 minutes per side. Remove from the pan and set aside.
Add water to a sauce pot. Bring to a boil and add salt. Then boil the pasta according to the package. Save ½ cup of pasta water.
If there is no olive oil remaining, add 1 tablespoon of olive oil. Then add the garlic to the pan and saute for 30 seconds. Squeeze in the juice from the lemon and pour in the white wine. Simmer for 5-10 minutes or until reduced by half. Stir in the cold butter until melted.
Remove the sauce from the stovetop. Stir in ½ cup of pasta water and then stir in the heavy cream slowly. Add the parmesan and parsley until completely combined. Return the shrimp to the pan and then stir in the pasta. Serve Immediately.
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Notes
Stir the heavy cream off the heat. It's okay if it curdles a little, just keep stirring. But if the sauce is still simmering, the heavy cream will separate.
Use a knife to slice the back of the shrimp to get a nice sear on the shrimp. You do this automatically when you devein shrimp but if you buy it already deveined, this can be a great way to improve the texture of the shrimp.
Sauce may appear thin at first. Stirring for a few minutes after cooking will help to thicken the sauce.