1. Preheat oven to 450°F. Heat 2 tablespoons oil in a medium saucepan and cook the onion and thyme 3 minutes. Add the rice and 2 cups water. Bring to a boil, cover and cook over low heat for 10 minutes, or until tender, adding the raisins during the last 5 minutes. Remove from heat, add the cheese and season with salt (in moderation) and pepper.
2. While the rice is cooking, remove seeds from squash and place cut side up on a foil-lined baking sheet. Brush cut sides with 1 tablespoon olive oil and sprinkle with salt (in moderation) and pepper. Roast until tender, about 20-25 minutes.
3. Fill the squash with the rice mixture and bake 20 minutes. Garnish with thyme sprigs and serve.