Wash the squash. Use water and a clean towel to remove any dirt from the outside of the squash.
Cut the squash in half lengthwise. Use a very sharp knife on a flat surface to safely cut the stem off the squash and then cut the squash in half from top to bottom lengthwise.
Scoop out the seeds. Remove the seeds and stringy pulp from the middle of the squash with a spoon.
Place the squash halves cut side down. Position each half flesh-down in a glass microwave-safe dish. The flesh of the squash should be touching the bottom.
Add one inch of water. This helps create steam inside the microwave.
Microwave on high for 20 minutes. Microwave times may vary slightly depending on the size of the spaghetti squash and the strength of your microwave oven. You know it's done when you can easily pierce the flesh with a fork and get spaghetti-like strands when scraped.
Let it cool. Use an oven mitt to remove the hot dish. Let the squash halves rest for a few minutes before handling.
Fluff with a fork. Turn the halves over and gently scrape the spaghetti-like strands from the flesh of the squash.
Season and serve. Add a little olive oil, parmesan cheese, or your favorite pasta sauce to complete the dish.