Preheat oven to 375

Line an 8" cake pan with parchment and grease well

In a bowl, mix the sugar, eggs and vanilla. Set aside.

In a double boiler over low heat, melt the chocolate and butter, stirring occasionally.

Add the melted mixture to the egg mixture

Gently fold in the cocoa powder.

Pour into prepared pan and bake for 25 minutes.

Allow to cool 5 minuted and invert onto a serving platter.

Once completely cooled, dust with powdered sugar.