Lightly grease and line the base and sides of a 20cm springform cake pan with baking paper.
Mix oil and sugar in a large bowl. Add eggs, 1 at a time, beating well after each addition, then stir in vanilla essence.
Combine almond meal, polenta, zest, and baking powder in a small bowl, then stir into the sugar mixture. Pour into pan and bake for 50 minutes at 160 "C or until golden. Remove from oven, cool for 10 minutes in pan, then turn out onto a plate gently.
Meanwhile, to make syrup, combine all ingredients in a saucepan over medium-low heat. Cook for 10 minutes or until reduced and slightly thickened. Strain, discarding solids. Set aside to cool.
Brush the syrup generously over the cake and serve.