Wash the oranges and then place in a medium saucepan. Cover with water and bring to a boil. Reduce heat and simmer for two hours. You may need to add more water during this time to keep the oranges mostly covered. Remove from water and allow to cool.
Preheat oven to 375. Line a 20 to 28cm baking dish with parchment paper.
Cut out the ends of the oranges (to remove the white/bitter part). Place the oranges in a food processor and blend until you have a smooth consistency.
In a large bowl, add the eggs and sugar and whisk until combined. Add the blended oranges to the mixture, then the almond flour, baking powder and salt until all ingredients are well combined. Pour the mixture into the lined tin, then scatter over the almond flakes. Bake for 1 hour to 1 1/2 hours or until a toothpick comes out clean. The time will vary depending on the size of your tin. The cake should be golden on top.
Allow the cake to cool on a wire rack, then dust with icing sugar.
**From Marta Vodrey and Food on Paper