In a 6- or 7-quart cast iron Dutch oven, melt butter over medium heat. Whisk in flour; cook, whisking constantly, for 1 minute.
Whisk in milk, salt, garlic powder, onion powder, ground mustard, black pepper, and smoked paprika. Bring to a boil over medium-high heat, whisking constantly. Continue whisking until thickened, about 2 minutes. Turn off the heat and stir in the cheese until melted and completely smooth.
Add the cooked pasta to the cheese sauce and stir until just heated through. Taste and season with additional salt and pepper, if necessary. Serve!
