Cook the Pasta: Bring a large pot of salted water to a boil. Add the fettuccine and cook according to package instructions until al dente. Reserve 1/2 cup of pasta water, then drain the pasta and set aside.
Sauté Garlic: In a large skillet, heat the olive oil over medium heat. Add the minced garlic and sauté for about 1 minute until fragrant, being careful not to burn it.
Make the Cream Sauce: Pour in the heavy cream and bring to a gentle simmer. Whisk in the grated Parmesan cheese until melted and the sauce is smooth.
Add Flavor: Stir in the chopped cilantro, lime zest, and lime juice. Season with salt, pepper, and red pepper flakes if desired. If the sauce is too thick, add some reserved pasta water to reach your preferred consistency.
Combine Pasta and Sauce: Add the cooked pasta to the skillet and toss to coat it evenly in the creamy sauce. Allow everything to cook together for another 2-3 minutes so the pasta absorbs some of the flavors.
Serve: Plate the pasta and garnish with additional chopped cilantro, lime wedges, and more grated Parmesan cheese if you like.