Preheat your oven to 350°F (175°C) and prepare a 12-cup bundt pan by greasing it well.

In a large mixing bowl, whisk together the all-purpose flour, baking powder, salt, cinnamon, and nutmeg until evenly combined.

In the bowl of a stand mixer, beat the unsalted butter with brown sugar and granulated sugar until light and fluffy, about 3 to 5 minutes.

One at a time, add the eggs to the creamed butter and sugar, mixing well after each addition, then add the vanilla extract and mix until fully combined.

Gradually add the flour mixture to the stand mixer while alternating with the apple cider, mixing just until combined.

Pour the batter into the prepared bundt pan and smooth the top. Bake for 40 to 50 minutes, or until a toothpick comes out clean.

While the cake bakes, pour apple cider into a saucepan and bring to a boil, then reduce and let simmer until it thickens, about 10-15 minutes.

After removing the cake from the oven, allow it to cool in the pan for about 10 minutes before inverting it onto a wire rack. Brush the glaze over the top and sprinkle with cinnamon sugar.