Wash and boil the oranges whole for 1½ hours or until they are very soft.When cool enough to handle, cut them open, remove the pips, and puree the oranges, including the peels, in a food processor.
In a large bowl, beat the eggs with the sugar. Add the baking powder and almonds and mix well. Then mix thoroughly with the orange puree and pour into a buttered and floured cake tin – preferably non stick and with a removable base.
Bake at 170C fan/gas mark 5 for an hour. Let it cool before turning out.