Preheat oven to 350 degrees F (175 degrees C). Grease a 2 quart baking dish.
Bring a large pot of lightly salted water to a boil. Add macaroni and cook for 8 to 10 minutes or until al dente; drain.
In a medium saucepan, melt butter over medium heat. Stir in flour, salt, pepper, and garlic powder. Whisk in milk and cook, stirring constantly, until mixture thickens.
Stir in Cheddar cheese until melted. Remove from heat.
In the prepared baking dish, combine cooked macaroni with cheese sauce. Sprinkle with Parmesan cheese.
Bake for 30 minutes in the preheated oven, or until bubbly and lightly browned.