Preheat oven to 350 degrees F (175 degrees C). Grease a baking sheet.
In a large bowl, combine the flour, baking powder, and salt. Cut in the butter until the mixture resembles coarse crumbs. Stir in the buttermilk to make a soft dough.
On a lightly floured surface, roll the dough into a 12x9-inch rectangle. Place the dough on the prepared baking sheet.
In a medium bowl, combine the squash, cheese, rosemary, garlic powder, and nutmeg. Spread the mixture over the dough, leaving a 1-inch border around the edges.
Fold the edges of the dough over the filling, and pinch to seal. Cut 3 diagonal slits in the top of the braid.
Bake in preheated oven for 30 minutes, or until golden brown.
Interesting Facts
This recipe is a great way to use up leftover cooked squash.
Squash is a great source of vitamins A and C, as well as fiber.