Step 1

Line an 8" square or round cake pan with parchment paper or aluminum foil. Set aside.

Step 2

Preheat oven to 350 degrees F.

Step 3

In a large mixing bowl, whisk together flour, sugar, cocoa, soda, baking powder, and salt. Add egg, oil, and buttermilk and whisk well. Add hot water and whisk until the batter is smooth. Pour into prepared pan. Tap gently against the counter to release any air bubbles.

Step 4

Bake for 25 to 30 minutes OR until the toothpick inserted in few places comes out clean.

Step 5

Cool and make frosting in the meantime.

Step 6

To make the frosting, melt butter in a saucepan over medium-low heat. Add cocoa powder and whisk in. Cook for 2 minutes. Do not boil. Remove saucepan from heat. Add sifted powdered sugar and whisk in. Add vanilla and milk, one tablespoon at a time. The frosting should be shiny and smooth. Pour over warm cake and spread with a spatula. Let cool before cutting.