Preheat oven to 170 degrees C. Line a 20-23 cm round cake pan with a circle of baking paper. Grease the pan well.
In a bowl combine flour, cocoa powder, salt and baking powder. Stir carefully and set aside.In a mixing bowl beat eggs and sugar until foamy. Add olive oil, vanilla, coffee and sour cream and whisk until homogeneous. Gradually add the dry ingredients and whisk until absorbed.
Bake the cake for about 40 minutes or until a toothpick inserted in the center comes out clean. Remove the pan from the oven and allow the cake to cool for 10 minutes before transferring it to a wire rack. Let the cake cool well before frosting it.
Combine all ingredients in a mixing bowl and beat for 2-3 minutes, until homogeneous.
Top the cake with the frosting. Serve immediately or refrigerated.