Cook macaroni according to package directions until al dente, drain and set aside.
In a large skillet over medium heat, brown the sliced hot dogs for 3-4 minutes until slightly caramelized, then remove and set aside.
In the same pot you cooked the pasta, melt butter over medium heat and whisk in flour, cooking for 1-2 minutes to create a roux.
Gradually whisk in milk and continue whisking until the sauce thickens, about 5 minutes.
Remove from heat and stir in cheddar and mozzarella cheese until completely melted and smooth.
Add salt, pepper, and garlic powder, then fold in the cooked macaroni and hot dog slices.
Serve immediately while hot and creamy, or transfer to a baking dish and bake at 350°F for 15 minutes for a crispy top.