Preheat the oven to 350°F. Generously grease a 10- to 12-cup Bundt pan.

Add the apple cider to a small saucepan and simmer over medium heat until reduced to 1/2 cup, about 10 to 15 minutes. Set aside to cool.

In a medium bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, and salt.

In a large bowl, beat the softened butter, granulated sugar, and brown sugar until pale and fluffy.

Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract.

Stir the cooled reduced cider into the buttermilk.

With the mixer on low, add the dry ingredients in three additions, alternating with the buttermilk mixture in two additions. Begin and end with the dry ingredients and mix just until combined.

Spoon the batter into the prepared Bundt pan and smooth the top. Tap the pan lightly on the counter.

Bake for 45 to 50 minutes, until a tester inserted in the center comes out clean or with a few moist crumbs.

Cool the cake in the pan for 15 minutes, then invert onto a wire rack or serving plate. Let cool until just slightly warm.

For the topping, mix the sugar and cinnamon in a small bowl. Brush the warm cake all over with melted butter.

Sprinkle or pat the cinnamon sugar over the cake, then let the coating set slightly before slicing and serving.