Update, 08/24/2014: Reduced the butter and sugar and it still turned out well — I used 10 Tablespoons butter, instead of 16 Tbsp [2 sticks] and 1-1/3 cups sugar, instead of 2 cups I really like it with the lesser amount of sugar. It is still a very moist, dense cake. I also found a new glaze recipe, which is listed below. The order of steps have been revised so that you melt the butter first, giving it time to cool.
Cook’s notes: This cake is so good that I once made it 3 times during a two-week period. It fetched $55 at a silent auction for charity. It is very similar to a Nigella Lawson version baked in a spring-form pan, but a Bundt pan is easier to deal with. The cake is so moist that it doesn’t need a ganache glaze, cream cheese frosting, or even a sprinkling of powdered sugar. It tastes wonderful served plain.
10 Tbsp unsalted butter
1 cup stout (such as Guinness Extra Stout)
3/4 cup unsweetened cocoa powder (preferably Dutch-process; preferably Double-Dutch Dark Cocoa by King Arthur) — to make the cake extra-dark, use 1/4 cup black cocoa by King Arthur and 1/2 cup Dutch-process cocoa
2 cups all purpose flour
1-1/3 cups white sugar
1.5 teaspoons baking soda
3/4 teaspoon salt
2 large eggs
2/3 cup light sour cream
Heat oven to 350F. Coat a Bundt pan with cooking spray or melted butter well; make sure you get in all of the nooks and crannies, especially the center cone.
Butter-stout mix: Melt the butter and bring it to simmer in heavy large saucepan over medium heat. Gently stir in the stout. Whisk in the cocoa powder until mixture is smooth. Cool slightly.
Flour mix: Whisk flour, sugar, baking soda, and 3/4 teaspoon salt in large bowl to blend.
Egg mix: In the bowl of a stand mixer, beat eggs and sour cream to blend. Pour in the cooled butter-stout mix and beat just to combine. Add flour mixture in two batches, and beat briefly on slow speed after each addition.
Using rubber spatula, fold batter until completely combined. Pour batter into prepared pan.
Bake cake until tester inserted into center comes out clean, about 35 minutes. Transfer cake to rack; cool completely in the pan, then turn the cold cake out onto a rack.
Adapted from smitten kitchen
Combine 1 Tablespoon black cocoa, 2 Tablespoons Dutch-process cocoa, 2 Tablespoons melted butter, and 1 cup powdered sugar. The mixture will be pasty. Stir in 2 to 3 Tablespoons hot water and stir to form a smooth glaze. Spoon over the top of the Bundt cake.