Preheat the oven to 160°C
Grease a 20cm springform tin, line the bottom and sides with greaseproof paper.
Beat the butter and sugar until light and creamy.
Beat in the egg then stir in the vanilla essence.
In a small bowl, mix the ground almonds, polenta, orange zest and baking powder.
Stir this into the cake mix.
Pour the mixture into the tin and bake for 40 to 50 minutes.
Remove the tin from the oven, leave to cool.
Crush the cardamom pods, then put all of the ingredients in a saucepan.
Simmer over a medium-low heat for about 10 minutes.
Set aside to cool.
Prick the cake all over with a skewer.
Brush generously with the syrup.