Preheat your oven to 350ºF (175ºC). Grease an 8-inch square baking pan with butter and line the bottom with parchment paper.

In a skillet over medium heat, reduce the apple cider for about 10-15 minutes until it thickens and measures to about ½ cup.

In a large mixing bowl, whisk together the sugar and eggs until pale and foamy, about 2-3 minutes.

Add the sour cream, melted butter, ground nutmeg, vanilla extract, and the reduced apple cider to the egg mixture, whisking until smooth.

Sift in the all-purpose flour, baking powder, and baking soda. Gently mix until just combined, being careful not to over-mix.

Pour the batter into the prepared baking pan and bake for 30-35 minutes, or until a toothpick inserted comes out clean.

Allow the cake to cool in the pan for about 15 minutes before transferring to a wire rack.

In a skillet, combine the remaining reduced apple cider, butter, sugar, and salt. Bring to a boil and simmer until thickened.

Drizzle the glaze over the cooled cake and sprinkle with a mixture of cinnamon and sugar.

Slice the cake into squares and serve warm with cider or coffee.