Preheat the oven to 400°F, adjust a rack to the lower third, and place a whole butternut squash on a baking sheet. Pierce it just a few times with a fork. Don’t do anything else!
Once the oven is preheated, place the baking sheet with the squash in the oven, and roast until it’s soft to the touch, about 1 hour, 45 minutes. After the first 45 minutes, turn it over and you should check on it every 20 minutes or so. When it’s done, the skin will be somewhat wrinkled with some charred areas, and some golden brown spots.
Let the squash cool so you’re better able to handle it. Then cut the stem end off.
Slice it in half lengthwise. Be careful because it’s still hot, a lot of steam will release at this point.
Use a large spoon to gently scoop out the seeds and membranes. (Keep the seeds — just like those from a pumpkin, they can be roasted and seasoned. Just put them in a fine mesh strainer and rise them, removing any of the squash membranes that might be stuck.)