Preheat the oven to 375F (190C).

To make the cake, stir together the almond flour, cocoa powder, sweetener, baking powder and salt.

Stir in the Diet Coke. It will froth up but will soon calm down after you have combined it.

In a separate bowl, whisk two egg whites together until soft peaks form. Gently fold them into the rest of the mixture.

Spoon the cake batter into a 9" springform cake tin. Bake in the oven for 20 minutes or until the center of the cake is cooked. Leave to cool for 5 minutes then transfer to a wire cooling rack.

To make the ganache frosting, melt the unsweetened chocolate in the microwave.

Leave to cool for 5 minutes, then whisk in the heavy cream, softened unsalted butter, and low carb sweetener. Keep whisking until the mixture is smooth and fluffy.

Spoon the frosting onto the cooled cake.