1. Preheat your oven to 350°F (180°C). Butter a 10-cup (2.5 L) Bundt pan.
2. In a large bowl, whisk together flour, sugar, cocoa powder, baking powder, baking soda, cinnamon, nutmeg, cayenne and salt. In a medium bowl, whisk together milk, butter, eggs and vanilla. Pour the milk mixture over the dry ingredients, whisking until smooth (the batter is liquid).
3. Scrape into prepared pan. Bake for 35 to 40 min or until a cake tester inserted in the center comes out clean. Let cool in pan on rack for 20 min. Invert the cake onto a rack and set it over a baking sheet to cool completely.
4. GLAZE: Meanwhile, whisk together cocoa powder continuously, and bring to a boil. Reduce heat and cook, occasionally whisking, for 30 sec until thickened. Whisk in vanilla.
5. Pour over the cake, letting excess drip down the sides. Let cool.