1. Bring a large pot of salted water to a boil. Cook the fettuccine according to package instructions until al dente. Drain and set aside, reserving 1 cup of pasta water.
2. In a bowl, toss the shrimp with Cajun seasoning until evenly coated.
3. In a large skillet over medium heat, heat the olive oil. Add the shrimp and cook until pink and opaque, about 2-3 minutes per side. Remove from the skillet and set aside.
4. In the same skillet, melt the butter over medium heat. Add the garlic and sauté until fragrant, about 1 minute.
5. Stir in the heavy cream and bring to a gentle simmer. Add the Parmesan cheese, salt, and pepper, stirring until the cheese has melted and the sauce is smooth.
6. Add the cooked pasta to the skillet, tossing to coat evenly with the sauce. If the sauce is too thick, add reserved pasta water a little at a time until desired consistency is reached.
7. Return the shrimp to the skillet and toss to combine. Cook until everything is heated through, about 2 minutes.
8. Garnish with fresh parsley and serve with lemon wedges if desired.

Just like my abuela taught me, trust your senses as you cook. The sauce should be silky and fragrant, a beautiful blend that clings to each strand of pasta.