Bring a large pot of salted water to a boil. Add elbow macaroni and cook until al dente, about 8 minutes. In the last 2 minutes, add broccoli florets. Drain and set aside.
In the same pot, melt butter over medium heat. Whisk in flour and cook for 1 minute. Gradually add milk, stirring until thickened, about 5 minutes.
Add garlic powder, onion powder, mustard powder, salt, and black pepper to the cheese sauce. Stir in cheddar and Parmesan until melted and smooth.
Combine cooked macaroni and broccoli with the cheese sauce. Mix until well combined.
Transfer to a greased baking dish, top with extra cheese if desired, and bake at 350°F for 20 minutes until bubbly and golden brown.