Cooking spaghetti squash in the microwave steams the squash and the strands come out nicely — unlike cooking it in a conventional oven, which can cause the strands to bake to the skin. A simple quick fresh pesto is a snappy sauce for the steamed squash.
Prick the squash in 3 or 4 places with a fork, put it on a plate, and loosely cover it with plastic wrap. Microwave at full power for 9 minutes. Let the squash stand, still covered for another 5 minutes.
Meanwhile, make the pesto. Put the basil, cheese, oil, pine nuts, garlic, salt, and pepper in a food processor and pulse until well combined.
Halve the squash and scrape out the seeds. Using a fork, scoop the pulp into a large bowl. Add the pesto and toss to combine.