Preheat the oven to 180C. Grease and line a 10” square tin.
Zest 2 of the oranges and set aside in a bowl. Peel all of the oranges. Finely slice the fruit horizontally so you have a cross section of the segments. They should only be 5-7mm thick.
Arrange the slices on the bottom of the prepared tray making sure you over lap them.
For the sponge beat the butter and sugar until pale and fluffy. Add the eggs, yoghurt, flour and the zest to the mix and beat again until pale and batter like. Gently spoon over your oranges then spread level.
Bake for 45-50 minutes or until a knife inserted into the centre comes out clean. Set aside to cool completely before trying to flip.
Once cool turn the cake 180C and remove from the pan. Peel away the greaseproof gently and you should be left with a lovely pattern from the oranges. Slice into squares and serve with a dollop of yoghurt and curd each. I like to add a sprinkle of coconut to the cake too.