Mix together the cake mix, eggs, melted butter, Eggnog, nutmeg, and rum extract with a stand mixer or hand mixer. Then whip the ingredients for 2-3 minutes until the batter is light and fluffy.
Prepare the bundt pan by spraying it with nonstick cooking spray, then sprinkle with sugar, completely coating the pan. Pour the eggnog cake batter into the bundt pan and bake at 350 degrees for 35-40 minutes or until a toothpick inserted comes out clean.
Remove the cake from the oven and allow it to cool in the pan on a cooling rack for about 20 minutes. Place a cooling rack over the pan and invert to remove the cake from the pan. Allow the cake to completely cool, then serve.
Optional Eggnog Frosting: In a mixing bowl, beat together the cream cheese and butter. Add the powdered sugar, eggnog, vanilla extract and nutmeg. Add to a piping bag and pipe over the top of the cooled cake and serve.