Cut squash in half lengthwise, scoop out seeds and fibers. Place in a microwave safe dish and cover. Microwave 8-9 minutes. Can also be baked at 350 degrees for one hour. When done, scoop out flesh with a fork into a large bowl.
In an electric blender combine basil, garlic, olive oil, Parmesan cheese, salt a pepper and puree until smooth.
Combine pesto with 4 cups spaghetti squash (save any remaining squash for another recipe). Add tomatoes and season with additional salt and pepper. Serve.