Take the butternut squash and pierce it all over with a fork. Put it in the microwave for five minutes.
Cut the squash in half, remove the seeds and pulp. Cut the skin off with a knife or vegetable peeler (be careful the squash will be hot, use a towel to hold it while you cut). Cut the peeled squash into ½ inch cubes.
Cover a baking sheet with aluminum foil and pour the olive oil on it. Put the squash cubes on the baking sheet. Add the salt, pepper, and sage. Use your fingers to completely coat the squash with the oil and seasonings. Spread the coated squash evenly in a single layer on the sheet.
Bake at 400° F for 25-30 minutes, until squash is easily pierced with a fork.