Cook pasta according to package directions. Drain and set aside, covered.
In the meantime, prep your sauce. As mentioned prior, the mix cooks fast and you must be attentive to prevent any components from burning. I'd measure out the milk in a glass measuring cup with a spout for easier pouring - optional, but very useful in this case. When you're ready: Heat a nonstick or cast iron skillet to medium.
Melt butter or heat oil. Add flour and whisk for one minute until thoroughly combined with your fat. SLOWLY pour milk in a steady stream while whisking constantly until milk is spent and no clumps of flour are visible in the pan, about one more minute. Bring the mix to a soft boil and whisk until just starting to thicken, the consistency of a somewhat watery pudding.
Add your pumpkin and half of the cheese and whisk until cheese melts. Measure and add onion powder, garlic powder, nutmeg, and the rest of the cheese and whisk to combine. Turn off the heat. Add salt and pepper to taste. When you are satisfied with the level of spice and savoriness, pour in your pasta and toss until each noodle bathes in the cheese sauce.
Serving suggestions: fish, roasted or steamed broccoli, crunchy salad with nuts and cranberries, or on its own with some breadcrumbs and a touch of minced thyme.