Preheat the oven to 180°C / 350°F. Have a large round bundt or tube pan ready (do not grease).

Separate the 5 eggs into yolks and whites, placing the whites in a clean, dry bowl for whipping and the yolks in a separate bowl.

Measure out the sugar: set aside 70 g for the egg whites and 180 g for the yolks.

Using a stand mixer or hand whisk, beat the egg whites until soft peaks form. Gradually add the 70 g sugar while continuing to whisk until stiff, glossy peaks form. Transfer the whipped whites to a clean bowl and set aside.

In the mixer bowl, beat the egg yolks with the remaining 180 g sugar for about 3 minutes, until the mixture is pale and creamy.

In a separate bowl, sift together the 250 g cake flour, 1 tsp baking soda (bicarb), and a pinch of salt.

In another small bowl, combine 125 ml olive oil, the zest of one orange, 8 Tbsp squeezed orange juice, and 4 Tbsp milk.

Add the dry ingredients and the olive oil mixture to the egg yolk mixture alternately, beginning and ending with the dry ingredients (for example: one-third dry, half wet, one-third dry). Mix briefly after each addition until just smooth; do not overbeat.

Gently fold the whipped egg whites into the batter in three additions. Use a spatula and fold carefully to keep as much air as possible; stop folding when no large white streaks remain.

Pour the batter into the ungreased bundt or tube pan and smooth the top lightly.

Bake for 45–50 minutes, until the cake is springy to the touch and a sharp knife or skewer inserted into the center comes out clean. If the top is browning too quickly, loosely tent with foil halfway through baking.

Remove the cake from the oven and allow it to cool in the tin completely before unmolding.