Pop the oranges in a medium-sized saucepan and cover with water. Place over a medium heat and bring to the boil. Boil for about 1 ½ hours - or until they are very soft. Alternatively, pierce the oranges all over and cut a cross on the tops. Place in a microwave-safe bowl with a splash or water, cover with cling film and microwave for about 8-10 minutes or until softened. Whichever method you use, remove the oranges to a separate bowl and leave until cool enough to handle.

Preheat the oven to 170C Fan and grease and line a 23 cm loose-based tin with non-stick baking paper. 

Slice open the oranges and remove the pips. Tip into a food processor (peel included) and blitz until you have a smooth purée.

In a large mixing bowl, beat the eggs with the sugar until fluffy. Add the baking powder and ground almonds and mix well until combined. 

Mix in the orange purée until combined, then pour into the prepared tin. Bake for about 1 hour - or until well risen and golden. Leave to cool in the tin for at least 20 minutes before turning out onto a wire rack to finish cooling completely.  

Dust with icing sugar, sprinkle with orange zest, cut into slices and serve. Enjoy!