A butternut is the most forgiving thing in the shop and the one most often left in the bowl until it is too late. It keeps a month, which is exactly why nobody gets round to it.
Roast it in wedges with the skin on at 200°C for forty minutes: the skin softens and there is no peeling. Or cube it and let it collapse into a soup with onions and stock, which takes twenty-five minutes and freezes well.
The seeds are worth keeping. Rinse them, dry them, toss them in oil and salt and give them ten minutes in the same oven as the squash.