Grease the mold with butter and cover the form with flour. Mix the egg yolks, water, castor sugar and vanilla sugar and stir well until frothy. Add pumpkin seed oil and stir until foamy.
Whisk the egg whites until stiff, then add the granulated sugar and stir.
Add a third of the egg white to the egg yolk mix and stir. Then, add the flour and baking powder and stir until smooth. Use a large spoon to gently mix the remainder of the egg white with the mix.
Bake at 160°C (320F) for one hour. Allow the cake to cool for 10 minutes and then plunge it gently onto a plate. Sprinkle some powdered sugar on top to finish.
