Bring a large pot of salted water to a boil. Cook the gluten free fettuccine according to package directions until just al dente. Reserve 1/2 cup of pasta water before draining. Set the pasta aside.
Season the chicken breasts on both sides with salt, pepper, and garlic powder. Heat olive oil in a large skillet over medium-high heat.
Add the chicken and cook for 6 to 7 minutes per side until golden brown and the internal temperature reaches 165 degrees F. Remove the chicken from the skillet and let it rest for 5 minutes, then slice into strips.
In the same skillet, reduce heat to medium and melt the butter. Add the minced garlic and cook for about 1 minute, stirring constantly, until fragrant.
Pour in the heavy cream and bring to a gentle simmer. Cook for 3 to 4 minutes, stirring occasionally, until the sauce starts to thicken slightly.
Reduce heat to low and gradually stir in the parmesan cheese until fully melted and smooth. If the sauce is too thick, add the reserved pasta water a splash at a time until you reach your desired consistency. Season with salt and pepper to taste.
Add the cooked fettuccine to the skillet and toss until every strand is coated in the creamy sauce. Serve topped with the sliced chicken and a generous sprinkle of fresh parsley.