Melt the butter in a large pot or Dutch oven over medium heat. Add the pumpkin spice, garlic and onion powders and cook for 2 to 4 minutes, stirring often, until the butter is very fragrant. Stir in the pumpkin and let it cook for a minute, while stirring.
Pour in the pasta, water and salt. Cover the pot and bring it to a boil over high heat. Once boiling, remove the lid and set the timer for 7 minutes.
Cook, stirring somewhat continuously. Once 7 minutes are up, turn down the heat and stirr in the cream cheese. Continue simmering until the cream cheese has melted in (I used whipped cream cheese)
Reduce the heat to low. Add the cheddar and Parmesan, and stir until the mixture is all combined.. Remove the pot from the heat.
Taste and add more salt if desired. This makes about 10 cups of mac and cheese, each cup is a serving!