Pat the cleaned shrimp dry with a paper towel, then season with a few pinches of salt, pepper, and ½ teaspoon Cajun seasoning.
Cook the linguine according to package instructions and set it aside.
Heat a large pan over medium heat.
Add the oil and butter to the pan.
Place the shrimp in a single layer and add the minced garlic. Cook for 2 minutes, then flip the shrimp and cook for another 1-2 minutes, or until they turn pink and are fully cooked.
Pour in the half-and-half and add the Parmigiano Reggiano.
Bring the mixture to a gentle boil, whisking continuously for about 2 minutes.
Turn off the heat.
Add the cooked pasta to the pan.
Stir in the diced tomato, chopped parsley, and the remaining ½ teaspoon Cajun seasoning.
Squeeze in the lemon juice, if desired. Be cautious, as lemon juice can cause dairy to curdle. Adding it with the heat off reduces this risk and enhances the flavor.
Mix everything well; the sauce will continue to thicken as it cools.
If the sauce becomes too thick or clumpy, add a splash of half-and-half to restore its creamy texture.
Serve immediately and enjoy!