Preheat oven to 350°.
Prepare an 8" round cake pan with a baking spray or shortening and flour pan for the cake to easily come out of the pan. you can line the pan with parchment paper if desired.
In a medium bowl or the bowl of a mixer, add the butter and sugar then whisk until well blended.
Add in vanilla, cinnamon, nutmeg, and egg and whisk to combine.
Add in cocoa, baking soda, salt, and stir in the flour with a spatula.
Add in buttermilk and stir, then add in the hot water and mix until smooth.
Pour the batter into prepared baking pan (wrap with a wet baking strip to bake the cake evenly)
Bake at 350° for 33-35 minutes or until a toothpick comes out clean.
Remove cake from oven and allow to cool for 10 minutes then place wax paper over the top of the cake to turn cake onto a cooling rack.
Cool the cake completely.