Place halved lengthwise and seeded squash halves, cut-side down, in a microwave-safe dish; add 2 tablespoons water. Microwave, uncovered, on High until flesh is tender, 10 to 15 minutes. (Alternatively, place squash halves, cut-side down, on a rimmed baking sheet. Bake in a 400 degrees F oven until tender, 40 to 50 minutes.) When cool enough to handle, scrape flesh into a large bowl with a fork. Let cool for 10 minutes.