Mix all dry ingredients and sift through a drum sifter.
Separate the egg white and yolk. In a mixer, whisk the egg whites until lightly fluffed-up. Slowly incorporate sugar into the egg white while whisking until it is smooth and silky with soft peaks. Once peaked, incorporate the yolks one at a time and continue whisking until fully incorporated
Add in the orange zest and sieved dry ingredients into the beaten eggs in three batches. Fold until it's evenly distributed before adding the next batch.
Add the remaining wet ingredients and lightly fold it.
Line the ring mould with oil and flour and wrap the base with parchment paper.
Preheat the oven at 160°C and pour the batter into the ring.
Gently tap out excess air bubbles and bake for 30 minutes.
Once done, remove from the oven and turn it over onto a cooling rack.
Once cooled, remove the cake from the ring and cut the cake into two pieces of 10 cm diameter with the thickness of 2 cm. Place them in the chiller.
In a blender, blend the remaining off-cuts into crumbs and lightly spread them out on a tray in the fridge to dry out.