Melt the butter in a large pot over medium-high heat. Add the onion and cook for 5 minutes until the onion begins to soften. Next, add the apples and squash. Cook stirring often for 8-10 minutes. Add the sage, garlic powder and flour, stirring well to incorporate. Next, add the hard apple cider and the broth, raise the heat to high and bring to a boil; after the mixture is boiling turn the heat down to a medium low simmer and cook covered, until the squash is soft, about 15-20 minutes.