In a large saucepan over a medium heat, gently warm up the water and 3 tablespoons of light brown sugar.
Slice your oranges into thin slices and add them to the sugary water and allow them to simmer over a low heat for 20-25 minutes. You want the rind to soften and start to go transparent.
Once that happens carefully remove your orange slices from the water and allow them to fully cool down on a plate. Increase the heat and reduce the syrup down until you have about 1/3 of the liquid left.
Once that is all done preheat your oven to 180C / 350F / Gas mark 4 and lightly grease an 8-inch cake pan and place a disk of parchment paper on the bottom and lightly butter the parchment paper.
Sprinkle over your 1 tablespoon of light brown sugar and gently place your cooled cooked orange slices over the disk of parchment until it is fully covered in orange slices.
In a medium-sized mixing bowl mix the flour, baking soda, baking powder and salt together, then place to one side.
In a stand mixer or in a large mixing bowl using an electric hand mixer cream together the butter and sugars until light and fluffy.
Beat in the eggs one at a time, then mix in the vanilla.
On a slow speed gently beat in half of the flour mixture.
Then add the creme fraiche and gently mix it in then add the remaining flour mixture and mix until everything is combined.
Pour the batter over the orange slices and smooth it out with a spatula.
Pop your cake into your hot oven and bake for 45 minutes. Some ovens (like mine) are slower and your cake may require a little more time. To stop your cake from over browning place some foil over the top of the cake and bake for a further 5-10 minutes.
After 45 minutes check your cake for doneness, if a pick comes out clean your cake is baked if not follow the above step.
Leave your cake to cool for 15-20 minutes in the tin before turning it out onto a wire rack and gently remove the parchment paper, if you want to add the extra syrup then do it now while the cake is still warm so it can soak all the way through. If you don't want to then just leave your cake to fully cool down to room temperature before storing this cake in an airtight tin.
This cake will keep well for up to 5 days when kept in a cool environment.