Wash the navel oranges and place into a large pot.
Cover with water and bring to the boil on the stovetop for 2 hours (add more water during this time).
Remove the oranges from the water and allow to cool completely (they'll be nice and soft).
Preheat oven to 160 degrees celsius (fan-forced).
Grease and line the base and sides of a 22cm springform pan with baking paper and set aside.
Cut the ends off the oranges and discard.
Chop the cooled oranges into pieces and place into a food processor.
Process until completely smooth and no lumps remain. Set aside.
Beat the eggs and caster sugar in a large bowl until pale and frothy (about 2 minutes on high using hand-held beaters).
Add the orange puree and stir through.
Add the almond meal and baking powder and stir through.
Pour the mixture into the prepared baking tin.
Sprinkle the flaked almonds over the top of the cake.
Bake for 60 minutes or until a skewer inserted into the middle comes out with just a few crumbs on it.
Allow to cool completely in the tin (preferably place it into the fridge overnight.
Sprinkle with icing sugar just before serving.
To make the vanilla bean double cream, place the cream, vanilla bean paste and icing sugar into a bowl. Mix together until well combined.
Spoon into a serving dish. Sprinkle with grated orange zest.