01 - Preheat the oven to 425°F. Line a baking sheet with parchment paper.
02 - In a large bowl, combine butternut squash cubes, apple slices, and red onion with olive oil, thyme, salt, and black pepper. Toss thoroughly to coat.
03 - Spread the mixture evenly on the prepared baking sheet. Roast for 20 to 25 minutes, stirring once halfway through, until the squash is tender and lightly caramelized. Allow to cool slightly.
04 - While vegetables roast, combine flour and salt in a food processor or large bowl. Add cold butter and pulse or cut in with a pastry blender until the mixture resembles coarse crumbs. Gradually add ice water, mixing just until the dough forms a cohesive ball. Shape into a disk, wrap in plastic, and refrigerate for 20 minutes.
05 - On a lightly floured surface, roll the chilled dough into a 12-inch circle. Transfer to a parchment-lined baking sheet.
06 - Arrange the roasted squash, apples, and onions in the center of the dough, leaving a 2-inch border. Drizzle honey or maple syrup over the filling and sprinkle crumbled cheese if using.
07 - Fold the dough edges over the filling, pleating evenly to form a rustic border. Brush the crust with beaten egg and sprinkle with coarse sugar if desired.
08 - Bake for 25 to 30 minutes or until the crust is golden brown and crisp. Allow to cool slightly before slicing and serving.