Heat the oven to 375°. Cut the squash in half and scoop out the seeds. Place on a cookie sheet and brush with a little of the butter and season with a little salt. Place a thyme sprig in each half and bake for 15 minutes. Meanwhile, mix together the apples, the remaining melted butter, the sugar and the cinnamon. Remove the squash from the oven. Fill each squash with the apple mixture. Put them back in the oven for 15-20 minutes more, or until the squash and the apples are soft and caramelized.