Preheat the oven to 170 C. Grease a 9 inch springform tin and set aside. You can use a regular round cake tin as well but it's easier to slice the cake in a springform tin.
Sift the cocoa into a small bowl and pour the boiling water over it. Whisk to combine into a smooth liquid. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment (or you could use a mixing bowl and hand mixer as well), combine the olive oil, sugar, vanilla and eggs. Beat on medium speed for 2 to 3 minutes until slightly thicker, paler and frothy. You don't need to beat this mixture until the eggs are super thick and airy unlike with a traditional sponge cake, because there's baking soda in this batter which will help it rise anyway.
Pour in the liquid cocoa mixture and beat to combine. Add the ground almonds, then sift in the flour, baking soda and salt. Beat again briefly on low speed to combine until you have a smooth, runny batter.
Pour the batter into the prepared tin, smoothen the top and bake for 40 minutes until a toothpick poked in the center comes out with moist crumbs, no wet batter. The center will look a little darker than the edges and a little puffy. Let the cake cool for 5 minutes in the oven itself (the center will fall slightly but shouldn't sink).
Allow the cake to cool in the tin for an hour, then dig in while still warm! Store in an airtight tin at room temperature for 2 to 3 days and then in the fridge for a week. Best eaten at room temperature or lightly warmed up with a drizzle of cream on top! Happy baking :)