Butter a 10x3 inch bundt pan, lightly coat in with nonstick spray, then flour it, tapping out the excess flour.
Sift together the flour, baking powder, salt and nutmeg and set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium speed until creamy and smooth.
Add the sugar and beat om medium speed until light in color and fluffy, about 5 minutes.
Add the eggs 1-2 tablespoons at a time and beat on medium speed until incorporated.
On the lowest speed, add the flour mixture in four additions alternately with the eggnog in three additions, beginning and ending with the flour mixture and mixing after each addition until incorporated. Add the vanilla.
Pour batter into the prepared pan. Bake for 55-65 minutes or until top springs back when lightly touched in center.
Let cool on wire rack for about 10 minutes. Invert a wire rack on top of the cake, invert the cake onto it and carefully lift off the pan.
For the glaze: In a small bowl, combine the sugar, rum and water and stir with a rubber spatula just until blended.
Using a pastry brush, coat the top and sides of the warm cake cool before serving.