Slice the spaghetti squash in half. Using a spoon to scoop out and discard seeds from the middle of each half.
Arrange squash in a 9x13-inch casserole dish, cut sides down. Pour 1 cup water into the dish and bake until just tender, 30 to 35 minutes. Using a fork, rake it back and forth across the squash to remove its flesh in strands. You'll soon begin to see "spaghetti" formed! Enjoy immediately or store in an airtight container for up to 3 days.