In a large pot, bring salted water to a boil. Add the fettuccine pasta and cook according to package instructions until al dente. Reserve 1/2 cup of pasta water, then drain and set aside.
In a bowl, toss the peeled shrimp with Cajun seasoning until evenly coated.
In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add the seasoned shrimp to the skillet and sauté for 2-3 minutes on each side until they turn pink and are cooked through. Remove shrimp from the skillet and set aside.
In the same skillet, add the remaining tablespoon of olive oil and minced garlic, sauté for 30 seconds until fragrant. Pour in the heavy cream, stirring to combine. Bring to a gentle simmer.
Gradually whisk in the grated Parmesan cheese until melted and the sauce is smooth. If the sauce is too thick, add reserved pasta water a little at a time until you reach the desired consistency.
Add the cooked fettuccine and sautéed shrimp back into the skillet. Toss everything together until the pasta is well coated with the Alfredo sauce. Season with salt and black pepper to taste.
If using, add cherry tomatoes for a fresh burst of flavor. Stir in chopped parsley just before serving.
Notes
Serve the pasta in shallow bowls, garnished with extra parsley and a sprinkle of Parmesan cheese on top for an inviting look.