Bring a large pot of water to a boil and salt it. Cook the pasta making sure it's not quite al dente (so about 1 minute less than the cooking time, because you'll be combining in pan with the sauce and heating together and it will cook a little more).
While the pasta is cooking, prep the pumpkin sauce.
Heat 2 tablespoons olive oil in a large skillet over medium heat. Add onions and season with salt and pepper. Cook, stirring occasionally, until the onions have become translucent and have totally softened, 5 to 8 minutes.
Add the wine (water, if you’re not using wine), cinnamon, nutmeg, and simmer until it reduces (about 3-5 minutes). Stir in the pumpkin puree and add in the milk. Stir to combine. Check seasoning, and add some more salt and pepper, if needed.
When pasta is cooked reserve some of the pasta water (1/2 cup is good), drain well and immediately add the pasta to the pan with pumpkin sauce. On medium heat, give it a nice stir to combine it all together. If it’s too thick, loosen it with a little bit of the reserved pasta water and stir it all together.
Spoon it out onto plates. Add some more crushed black pepper (if you like). Sprinkle on the chopped fresh sage. Enjoy!