Combine all the dry ingredients in a bowl with a whisk.
In a large owl, whisk together all the wet ingredients until well combined.
Add the dry ingredients and stir until just combined, do not over mix.
Rub the sides and bottom of a 9” round baking tin with butter. Sprinkle flour and tap all around such that the whole tin is covered with a thin layer of flour.
Scrape out the batter into the prepared tin and smoothen out the top.
Preheat the oven at 180°C.
Divide the orange into segments, carefully slicing each segment into halves. Decorate the top of the cake with the prepared orange segments. Sprinkle a spoon or two of granulated sugar over this.
Keep the tin in the preheated oven and bake at 180°C for 40 minutes, rotating the tin once at the 20 minute mark for even browning.
If needed cover the cake with a layer of aluminium foil after 30 minutes to ensure that the centre of the cake doesn’t remain wet.
Cool in the tin for 10 minutes. Carefully unmould and allow to cool on a rack for 20 minutes or so before proceeding to slice.
