Preheat oven to 350°F. Grease and Flour three 9" round cake pans.
In a medium bowl whisk the flour, baking powder, baking soda and salt together.
In a large heatproof bowl, combine the unsweetened chocolate and cocoa powder. Heat the water and butter in a pot over medium heat until butter is melted but water is simmering not boiling.
Pour hot liquid over chocolate and cocoa mixture and stir to combine and melted and smooth.
Add the sugar and mix to combine. Make sure chocolate mixture has cooled then add the eggs, one at a time and use a hand mixer to just combine. Add vanilla extract.
Add the flour mixture to the chocolate mixture alternating with the buttermilk, finish with the flour, being sure to scrape down the sides. Don’t over mix.
Divide batter evenly between the prepared pans. Bake 20-30 minutes until a toothpick comes out clean.
Cool in pan 15 minutes, then invert and cool on rack. Cool completely before frosting.