Place oranges in large saucepan and cover with water. Place over high heat and bring to the boil.
Reduce heat and leave to simmer for 1 hour, ensuring that oranges are covered with water the whole time.
Remove oranges from saucepan and set aside to cool.
Preheat oven to 170°C. Grease a round cake tin.
Once cooled, cut oranges into quarters and remove seeds.
Place in a food processor and blend until as smooth as possible.
In a large mixing bowl, beat eggs and Natvia stevia blend with an electric beater, on medium speed for 2-3 minutes, or until mixture becomes thick.
Add oranges, baking powder and almond meal and mix with a wooden spoon until combined.
Pour into the prepared cake tin and bake for 1 hour.
Remove from oven, leave in tin for 20 minutes, then turn out onto a wire rack to cool. Serve dusted with Natvia Icing.