Preheat the oven to 325 degrees, Grease and flour three (8x2 inch) cake pans. You could also use two 9x2 inch pans. We like to line the bottom of each pan with a circle of parchment paper.
Add espresso powder to hot water, stir to dissolve, and set aside.
In the mixing bowl, combine the dry ingredients: cake mix, sugar, flour, and pudding mix. Whisk to blend.
Next, add the eggs, sour cream, vegetable oil, and espresso mixed with the hot water.
Using an electric mixer (fitted with a paddle attachment if using a stand mixer), mix on low speed for 30 seconds to blend. Then, increase to medium speed and mix for two minutes, stopping to scrape down the sides as needed.
Divide the batter between the three prepared cake pans.
Bake at 325 degrees for 22 minutes - Times may vary. When the center of the cake layer springs back when lightly touched, or a toothpick can be inserted and removed with just. a few crumbs attached, the layers are done! (See notes for additional bake times/pan sizes)
Place the cake layers (still in pans) on a wire rack and cool for 5 minutes before turning out.