Preheat your oven at 180C and grease a bundt pan, or a regular cake pan with tahini or butter and flour. Teta says tahini.
In the bowl of a stand mixer fitted with the padle attachment, or handheld whisk (doing it by hand will take you ages) mix the egg yolks, sugar, and vanilla on high until pale and fluffy
Add the orange zest, oil and butter and mix until just incorporated
Add the flour and baking powder and mix until combined
Add the juice and mix
With a hand held whisk, whisk the egg whites for around 2-4 min or until they become white, soft, and frothy
Fold into the cake batter gently, do not deflate them
Pour into cake pan and bake for 40 min or until a skewer inserted comes out clean
Do not flip before it cools down COMPLETELY
Enjoy