Method

• 1.
  Preheat oven to 180°C/160°C fan-forced. Grease base and side of a 7cm-deep, 20cm round springform cake pan, then line base with baking paper. Sprinkle both sides of orange slices with 2 tsp of the extra sugar, then arrange in a single layer over base of prepared pan.
• 2.
  Sift flour, baking powder and bicarb three times over into a large bowl. Using a stand mixer fitted with the paddle attachment, cream the butter with the sugar on medium-high speed for 10 minutes until light and fluffy (the sugar won’t be totally dissolved). Add the eggs, one at a time, mixing well on medium speed between each addition. Reduce speed to low and gradually drizzle in the oil, mixing constantly until it forms a mayonnaise consistency. Then, gradually mix in the buttermilk until well combined.
• 3.
  Add sifted dry ingredients in 3 batches, mixing well after each addition, to create a smooth and thick batter (do not overmix). Carefully spoon batter over the oranges in the prepared pan, trying not to disturb their placement. Level top using a spatula. Sprinkle top evenly with the remaining 2 tsp extra sugar. Bake for 30-40 minutes until cooked when a skewer inserted in the centre comes out clean and top is golden.
• 4.
  Release cake from pan and invert the hot cake onto a wire rack, orange slices facing up, to cool completely and develop a crust. Once cooled, using a large serrated knife, carefully split cake horizontally into two layers. Place the cake base (without orange slices) on a serving platter, then dollop with whipped cream and spoon over jam. Top with the other cake half, orange slices facing up.
• 5.
  Serve cake scattered with raspberries and edible flowers, if using, and lightly dusted with icing sugar.