Roast spaghetti squash whole (see footnotes for other methods)
Preheat oven to 375°F.
Pierce spaghetti squash skin in a few places with a paring knife.
Place whole squash in a baking dish and bake 40 minutes. *See recipe footnote
Carefully remove the cooked squash from the heat source. Test for doneness by inserting a paring knife through the shell and into the hollow center. If any resistance occurs, continue cooking the squash in short increments until it passes this test.
Transfer fully cooked squash to a cutting surface.
Use your preferred knife to cut off the stem. Then cut the whole squash lengthwise for shorter strands or crosswise for longer strands.Note: this can be done while the squash is warm or cooled down.
Scoop out the seeds. Use a fork to pull the noodle strands away from the sides until all strands have been removed.
To store, allow squash noodles to cool and refrigerate in an airtight container up to 5 days.
Notes
If you like your baked squash caramelized, here's a trick. At the 20 minute mark, remove the squash from the oven, cut in half, remove the seeds, coat each half with olive oil, and bake face down in the dish another 20 minutes. Continue with step 7 in the recipe.
Microwave whole spaghetti squash
Use a paring knife to carefully pierce the squash through to the center cavity in several places.
Microwave the whole squash in a microwave-safe baking dish on HIGH for 3-5 minutes until it's soft enough to cut.
Transfer squash to a cutting surface and carefully cut lengthwise or crosswise (Caution: it will be hot).
Place squash halves face down in the baking dish and add ¼ inch water.
Microwave the squash in 3-5 minute intervals until cooked through.