Preheat your oven to 160°C (320°F).
Ensure your tube pan is clean and dry, but do not grease it.
Carefully separate the egg yolks from the whites.
In the bowl with the egg yolks, add the castor sugar, cake flour, baking soda, and a pinch of salt. Whisk together until well combined.
Add the olive oil, orange zest, orange juice, and milk to the dry ingredients. Mix until smooth and well combined.
Using an electric mixer, whip the egg whites on high speed until stiff peaks form.
Gently fold the whipped egg whites into the yolk mixture in three additions.
Pour the batter into the prepared tube pan and smooth the top with a spatula.
Bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove the cake from the oven and invert the pan onto a cooling rack. Let it cool completely in the pan.
Once the cake is cool, gently run a knife around the edges and the center tube to release it from the pan. Turn it out onto a serving plate.
