Preheat oven to 170 degrees celsius (fan-forced). Grease a 23cm round tin and set aside.
Sift the flour, sugar, cocoa powder, baking powder, bi-carbonate soda and salt into a bowl and set aside.
Using beaters or a stand mixer, mix the buttermilk, oil, room temperature eggs and vanilla in a large bowl until well combined.
Slowly add all of the dry ingredients to the wet ingredients with the mixer on low. Pour in the coffee and mix until well combined.
Pour the batter into the prepared tin and bake for approximately 35 minutes or until a toothpick inserted in the centre comes out clean (don't overcook the cake - you want it to be nice and fudge-like!).
Allow to cool completely.