Instructions

1. * If using large oranges, you’ll need about 11 slices in total for the top which you should get from 2 oranges, otherwise, 3 smaller ones should do.
2. Line the bottom of a 23cm (9inch) round springform tin with parchment paper and grease the sides with butter. Set aside.
3. For the orange topping, combine the sugar and water in a large shallow saucepan and set over medium heat. Stir until the sugar has dissolved.
4. Add the rosemary and orange slices to the pan and partially cover with a lid then simmer gently over medium low heat, turning sliced over once or twice, until the rinds have softened, 10-15 minutes.
5. Arrange the orange slices in the bottom of the prepared springform tin, starting with 1 slice in the centre, 5 around it like the petals of a flower, and the remaining 10 slices around the outside against the edges of the tin. Set aside until needed, also reserving the orange-infused syrup for later.
6. Pre-heat oven to 180°C / 160°C fan assisted.
7. To prepare the cake, whisk together the flour, polenta and baking powder in a large bowl then whisk together the remaining ingredients in a separate bowl or large jug.
8. Add the wet ingredients to the dry and mix with a wooden spoon or electric mixer just until the batter is smooth, scraping down the sides of the bowl with a spatula as needed.
9. Pour the batter into the tin on top of the oranges then bake in the pre-heated oven until a toothpick inserted in the centre of the cake comes out without any wet batter clinging to it, 45-48 minutes.
10. While cake is still warm, pierce the sponge in various places with a small sharp knife or prick with a skewer and spoon or brush about 1/3 of the reserved syrup over the cake.
11. Leave cake to cool in the tin on a wire rack for about 20 minutes.
12. Run a sharp knife around the sides of the sponge then remove the collar of the springform tin from the pan. Place a serving plate on top of the sponge and flip the cake over. Remove the base of the springform tin then carefully peel away and discard the parchment paper.
13. While the cake is cooling completely, place the remaining orange-infused syrup over medium heat and simmer until reduced slightly and it has thickened. Remove from heat and leave to cool completely.
14. Before serving, spoon the syrup over the top of the cake and serve slices with a good dollop of whipped cream.
15. Store cake at room temperature in an airtight container for up to 3 days, or up to 5 days if kept in the fridge, though we do recommend allowing portioned slices to come to room temperature before enjoying.