Start by preheating the oven to 350F then generously grease a 10 cup or standard size bundt cake and set aside. I usually make my own cake goop recipe, and it always helps the cake come out of the pan so easily.
In a medium sized bowl, whisk together the sifted flour, cinnamon, nutmeg, salt, baking powder, and baking soda and set aside.
In a large measuring cup or medium bowl, mix the apple cider and the apple sauce together. and set aside.
In a large bowl, mix the oil, brown sugar, granulated sugar, vanilla extract, and eggs together until smooth.
Alternate between the dry ingredients and the apple cider mixture into the egg, oil, and sugar mixture. Make sure to begin and end with the flour, and don't overmix the batter!
Pour the apple cider donut batter into the prepared bundt pan. Bake in the preheated oven for 40-50 minutes or until a wooden skewer inserted in the center comes out clean. Cool the cake in the pan for 10 minutes before carefully inverting it onto a cooling rack.
Place the cooling rack over a large baking sheet, parchment paper, or wax paper, and brush the warm cake with the melted butter. Sprinkle generously with the cinnamon-sugar mixture and serve once the cake has fully cooled down.