Cut the onion in half (no need to peel). Lay the halves flesh-side down on the
baking sheet. Put the butternut squash on the
baking sheet. Roast the vegetables until the squash is tender enough that you can easily slide a paring
knife into it, testing in several places, 1 to 1 1/2 hours (time varies depending on size and shape of the squash). Remove from oven and set aside until the squash is cool enough to handle.