Carefully cut the squash in half lengthwise and remove seeds with a spoon. Discard seeds.
Place squash halves, cut side down, in a microwave-safe baking dish. Be sure the baking dish will fit in the microwave. Add ½ cup water to dish. Cover dish with plastic wrap, leaving corners uncovered.
Microwave on high for 15 minutes, or until squash is tender when pierced with a fork. Let cool 5 minutes.
Carefully remove plastic wrap. Using a fork, scrape the insides of the squash into long strings and place in a bowl. Discard skin.
Stir in tomato, Parmesan cheese, olive oil, and garlic powder.
Return squash to microwave. Microwave on high for 1 to 2 minutes or until warm. Serve.