In a large pot, bring salted water to a boil. Add the fettuccine pasta and cook according to package instructions until al dente. Drain and set aside, reserving 1/2 cup of pasta water.
In a bowl, toss the shrimp with Cajun seasoning until evenly coated.
In a large skillet, heat olive oil over medium-high heat. Add the seasoned shrimp and cook for about 2-3 minutes per side until they turn pink and opaque. Remove the shrimp from the skillet and set aside.
In the same skillet, add minced garlic and sauté for 1 minute until fragrant. Pour in the heavy cream and bring to a gentle simmer.
Stir in the grated Parmesan cheese and mix until the sauce is smooth. Add chopped spinach and sun-dried tomatoes, cooking until the spinach wilts, about 2-3 minutes.
Add the cooked fettuccine to the skillet, pouring in the reserved pasta water to help combine everything. Toss to coat the pasta in the creamy sauce.
Return the sautéed shrimp to the skillet and gently fold them into the pasta and sauce mixture. Season with salt and pepper to taste.
Remove from heat and garnish with chopped parsley before serving.