For the topping: 1/2 cup granulated sugar mixed with 1 tablespoon cinnamon
Instructions
Reduce the Apple Cider: Pour the apple cider into a small saucepan over medium-high heat. Simmer until the liquid has reduced to exactly 3/4 cup. This should take about 10 to 15 minutes. Let it cool completely before using in the batter.
Prepare Oven and Pan: Preheat your oven to 350°F (175°C). Generously grease a 10-cup bundt pan with butter or non-stick cooking spray, ensuring you get into all the crevices. Dust lightly with flour and tap out the excess.
Whisk Dry Ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, and salt. Set this mixture aside for later.
Cream Butter and Sugars: In a large bowl or stand mixer, beat the softened butter, granulated sugar, and brown sugar together on medium-high speed until light and fluffy, about 3 to 4 minutes.
Add Wet Ingredients: Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract and the sour cream until well combined. Slowly pour in the cooled, reduced apple cider while mixing on low speed.
Combine and Bake: Gradually add the dry ingredients to the wet ingredients. Mix until just combined; do not overmix. Pour the batter into the prepared bundt pan and smooth the top. Bake for 45 to 55 minutes, or until a toothpick inserted into the center comes out clean.
The Donut Coating: Let the cake cool in the pan for 10 minutes before inverting it onto a wire rack. While the cake is still warm, brush the entire surface with melted butter. Generously sprinkle or press the cinnamon-sugar mixture all over the cake until it is fully coated.