How to Make It
Preheat the oven to 350°. Butter and flour a 10-cup Bundt pan. In a large bowl, sift the flour with the cocoa powder, baking soda and salt. In a standing electric mixer fitted with the paddle attachment, beat the softened butter until creamy. Add the granulated sugar and beat at medium speed until light and fluffy. Add the eggs, 1 at a time, beating well after each addition. Beat in the vanilla extract. At low speed, beat in the dry ingredients in 3 additions, alternating with 3 additions of the sour cream. Gradually beat in the boiling water.
Pour the cake batter into the prepared pan and bake in the lower third of the oven for about 65 minutes, or until a toothpick inserted in the center comes out clean. Let the cake cool in the pan for 5 minutes, then turn out onto a wire rack and let cool completely. Dust lightly with confectioners' sugar before slicing and serving.