Position a rack in the center of your oven and preheat to 350°F/177°C.
In a large bowl, sift together the flour, cocoa powder, baking powder and baking soda, and espresso powder. Stir in the salt.
In a large mixing bowl with an electric mixer (or a stand mixer fitted with paddle attachment), cream together the butter and sugar until light and fluffy, about 2 to 3 minutes on medium high speed.
Add the eggs one at a time, scraping down the mixing bowl well after each addition and mix until blended. Beat in vanilla until combined.
Add the flour mixture and sour cream alternately to butter-sugar-egg mixture, beginning and ending with the flour mixture until uniformly incorporated- do not overmix.
Grease and flour one 12-cup capacity bundt cake pan. I like to grease with melted shortening and dust with cocoa powder. You can also grease with non stick cooking spray with flour.
Pour batter into pan. Bake in a preheated 350°F degrees oven for approximately 50-60 minutes, until top is golden brown and when the cake is done when a toothpick or skewer inserted in the center comes out clean or with a few moist crumbs. Cool in the pan for 10 minutes, then invert on to a cooling rack.