Preheat your oven to 350 degrees F. Coat the inside of a 12-cup bundt cake pan with pan release (recipe below) or non-stick cooking spray.
In a large mixing bowl, whisk together the cake mix and nutmeg.
Add the eggnog, butter, sour cream, and eggs to the bowl. Use a hand mixer to beat everything together until it's evenly combined, about 2 minutes.
Pour the batter into the prepared bundt cake pan. Bake for 28-35 minutes or until a toothpick inserted halfway between the edge and tube comes out clean.
Remove from the oven and allow the cake to cool in the pan for 15 minutes. Then turn the cake out onto a serving plate or cake stand. Let the cake cool completely.
In a medium mixing bowl, whisk together the powdered sugar and eggnog to make the glaze. Add more eggnog as needed, 1/2 tablespoon at a time, until your desired consistency is reached. (I like the glaze to be thick enough that it looks pretty solid, but still has enough liquid that it slowly slides down the cake.)
Pour the glaze slowly over the top of the cake, allowing it to make its way down the sides. Allow the glaze to set up a bit before cutting the cake into slices and serving.
Notes
Pan Release: In a small bowl, mix 1 tablespoon vegetable oil + 1 tablespoon shortening + 1 tablespoon all-purpose flour until smooth and combined. Brush onto the baking dish or pan.For storing: Cover any leftovers at keep at room temperature for 2-3, in the fridge for 5-6 days, or freeze for up to 2 months.