Whisk the buttermilk, apple sauce, brown sugar, vanilla, and egg in a medium sized bowl.
Spray a baking sheet with cooking spray or line it with a silicone baking mat.
Combine the flours, baking powder, cinnamon, nutmeg, and salt in another large bowl, stirring with a whisk. Cut in the chilled butter with a pastry blender until small and crumbly. Fold in diced apples.
Add the buttermilk mixture to the flour mixture, stirring until just moist.
Place dough onto a floured surface and knead lightly four times with floured hands. Form dough into a 9-inch circle on the prepared baking sheet, about ¾" thick.
Using a bench scraper or knife (be careful if your dough is on a silicone mat), cut dough into 12 wedges all the way through. Leave dough in a circle for soft scones, or separate the triangles for crisp scones.
Bake for 18 to 20 minutes or until golden. Let cool 10 minutes.
Meanwhile prepare glaze by whisking the brown sugar into the melted butter, until dissolved. Add milk, cinnamon, and powdered sugar. Let rest at room temperature to thicken slightly. Drizzle glaze over the scones using a spoon. Glaze will harden as it sits. Store leftovers in an airtight container at room temperature.