1. Heat your oven to 160C/Gas Mark 4 and grease and line a 22cm springform cake tin.
2. Beat the butter and sugar together using an electric mixer or wooden spoon until light and fluffy.
3. Sieve the flour in a separate bowl and combine with the polenta and baking powder.
4. Beat each egg into the butter and sugar one at a time with a tablespoon of the flour/polenta mix. Once you have added all the eggs, fold in the remaining flour and polenta.
5. Stir in the orange zest and the juice of one of the oranges (leave the rest of the juice for the glaze). Pour the batter into the cake tin and bake for approximately 45 minutes. You can test whether it is done by putting a skewer through the cake – if it comes out clean then it’s ready.
6. Once the cake is baked, leave in the tin to cool.
7. To make the orange glaze, put the rest of the orange juice and the caster sugar in a small saucepan and heat through for about 5 minutes or until the sugar has dissolved.
8. Dot the cake with holes using your skewer and spoon the glaze over top until it seeps into the cake.
9. Only remove the cake from the tin when it has completely cooled.