Preheat the oven to 350°F (175°C) and generously grease and flour a 10- or 12-cup Bundt pan.
Whisk together flour, baking powder, baking soda, salt, cinnamon, and nutmeg.
Beat the softened butter, granulated sugar, and brown sugar until light and fluffy.
Add the eggs one at a time, mixing well after each addition.
Stir in the vanilla extract.
Add the dry ingredients alternately with the apple cider and sour cream, beginning and ending with the dry ingredients.
Gently fold the diced apple into the batter.
Pour the batter evenly into the prepared Bundt pan and smooth the top.
Bake for 48–55 minutes, or until a toothpick inserted into the thickest part comes out clean.
Let the cake cool in the pan for 10–15 minutes, then carefully invert it onto a wire rack.
Allow the cake to cool completely before glazing.
Whisk powdered sugar, apple cider, cinnamon, and vanilla until smooth.
Drizzle the cinnamon glaze generously over the cooled Bundt cake.
Let the glaze set briefly before slicing and serving.