Set the oven rack in the center and preheat to 325°F (163°C). Generously coat a 12-cup Bundt pan with butter, making sure to reach every groove and crevice. Then, lightly dust the pan with flour, shaking out any excess to prevent clumps. This ensures the cake releases smoothly after baking, giving you a perfect, clean finish.
In a medium bowl stir together the flour and baking powder.
In a large bowl, or the bowl of a stand mixer, combine the butter and sugar. Mix on low speed until the sugar is moistened, then turn the mixer to medium high and beat until light and fluffy.
Add the eggs one at a time, mixing until each is incorporated before adding the next. The mixture may split a bit, but it will come back together when you add the rest of the ingredients.
Scrape down the sides of the bowl then add nutmeg, vanilla, and salt and mix on medium speed until combined.
Add the sour cream and flour mixture in three additions each, and mix on low speed until combined, scraping down the sides and bottom of the bowl occasionally to ensure there are no dry pockets.
Transfer the batter to the pan and tap on the counter a few times to release any large air bubbles. Bake the cake until puffed, golden, and a skewer inserted into the center comes out clean or with a few moist crumbs, 50-60 minutes. Set the pan on a rack to cool.
While the cake is cooling, make the glaze. In a medium bowl, whisk the confectioners sugar, vanilla, 2 tablespoons milk, and salt together until smooth. The glaze should be the texture of runny honey. If it is too thick add a bit more milk. If it’s too thin add a bit more confectioners' sugar.
Let the cake cool in the pan set on a wire rack for 15 minutes, then invert it onto the rack.
Use a pastry brush to brush the warm cake with glaze. Then let the cake cool completely and brush the rest of the glaze over the top. Let the glaze set for 20 minutes before slicing.
