Preheat the oven to 350 degrees.
In a large mixing bowl, use a hand mixer on low to combine cake mix, apple cider, apple sauce, eggs, and melted butter.
Add brown sugar and vanilla and mix well.
Grease and flour a 10 or 12 cup bundt pan well and pour batter into the prepared pan.
Bake for 40-50 minutes or until a toothpick comes out clean (mine was done at 45 minutes).
Remove from the oven and let cool on a cooling rack for 15 minutes.
After 15 minutes, turn the bundt pan over onto a cooling rack or parchment paper.
Mix together cinnamon and sugar for the topping.
Brush butter over cake and sprinkle cinnamon and sugar topping on top and sides of cake.