Prepare the apple cider butter: Combine apples, light brown sugar and butter or oil in a medium saucepan over medium-high heat until mixture comes to a simmer. Reduce heat to low and cook, stirring occasionally, until mixture is reduced and appears soft and golden, 15 to 20 minutes.
Let mixture cool slightly, then transfer to a large measuring cup and add enough apple cider to make 3 cups/710 milliliters. Transfer mixture to a food processor or blender and purée until smooth. (This can be made up to 1 day ahead.)
Prepare the cake: Arrange a rack in the middle of the oven and heat to 325 degrees. Generously grease a 10-inch Bundt pan.
In a large bowl, whisk together flour, salt, baking soda, baking powder and cinnamon.
In another large bowl, whisk together eggs, prepared apple cider butter, honey, melted butter or oil and whiskey. Whisk in the dry ingredients until smooth.
Pour batter into prepared pan and bake for 50 to 60 minutes or until firm to the touch and a cake tester comes out clean.
Cool for 30 minutes, then carefully unmold cake and let cool completely on a wire rack.
Before serving, transfer cake to a platter and dust with confectioners’ sugar.