1. Preheat the oven to 350°F. Lightly grease cake pan of your choice, line with parchment paper, and grease the paper. 

2. Sift and stir together the dry ingredients: flour, 1 cup sugar, cocoa powder, baking powder, baking soda and salt in a container. 

3. Stir together the wet ingredients: milk, vanilla, oil, and mayonnaise (or sour cream) in a separate container. 

4. In a large mixing bowl, beat softened butter and 1 cup sugar together for 4-5 mins, until the mixture becomes light, airy and pale. 

5. Add the eggs, one at a time, to this mixture while whisking, making sure to scrape down the sides of the bowl between and after each addition. 

6. Starting with the dry ingredients, add the dry and wet ingredient mixtures to the butter, sugar, & eggs in an alternating pattern, in thirds until a homogenized mixture is reached.

7. Slowly pour the warm coffee to the side of bowl while stirring the batter. (Make sure the coffee is only lukewarm and not very hot or else the eggs in the batter will start to cook).

8. Transfer the batter to your pan(s). For a layered cake, divide the batter among the pans evenly by weight using a kitchen scale. 

9. Bake for approximately 35-40 minutes for a 9" x 13" pan; 30-35 minutes for 9" layers; 24-27 minutes for 8" layers, or 23 to 25 minutes for cupcakes.

10. Check to see that your cake has cooked completely by inserting a toothpick in the center. If it comes out clean, then the cake is done and is ready to be cooled. 

11. Cool completely at room temperature for 2-4 hours before decorating with buttercream frosting.