Preheat oven to 400° F. And line a baking sheet with foil to save time on cleaning.
Cut off the ends of the acorn squash so they sit flat and then cut the squash in half horizontally. Scoop out the seeds and arrange them cut side up on the baking sheet. Drizzle the flesh with olive oil and sprinkle with chili powder, salt and pepper. Place the baking sheet in the oven and roast the squash for 45 minutes or until tender.
While the squash is roasting make the filling. Heat a tablespoon of olive oil in a pan over medium-high heat. Add in the green onions and sauté for 2-3 minutes. Add in the remaining ingredients (except the cheese) and cook until heated through. Taste for seasoning.
Remove the squash from the oven and fill them with the rice mixture. Top with the shredded cheese and place them back into the oven for another 5 minutes or until the cheese is melted. Top with extra green onions and cilantro and serve.
