Preheat the oven to 350°F. Lightly grease two 8-inch round cake pans, dust lightly with flour and line the base with rounds of parchment paper.
Prepare the coffee and keep it hot.
Combine dry ingredients: sift flour, cocoa powder, baking powder and baking soda into a large bowl. Add both sugars and salt and whisk to blend well.
Combine wet ingredients: add eggs, oil, sour cream and vanilla to a medium bowl and whisk to blend well.
Make a well in the center of the dry ingredients, then pour in the wet ingredients. Mix until blended.
Add the hot coffee gradually in two stages and mix until evenly combined and the batter is smooth.
Divide batter evenly between the prepared pans and bake for 30-33 minutes until cakes spring back when pressed gently.
Transfer pans to a wire rack and let cool for 15 minutes before inverting the cakes onto the rack to cool completely.
Assemble the cake: once cakes are cooled, place one cake layer on a serving plate, spread frosting over the top, place the other cake layer on top, and cover the entire cake with frosting.
