Heat oven to 170°C fan. Grease and line the base and sides of a 22cm springform tin.
Combine the almond meal, polenta, sugar, baking powder and salt. Rub the orange zest into the mixture with your fingertips to release as much of the citrus oil as possible.
In another bowl, whisk together the eggs, melted butter, yoghurt, orange juice and vanilla.
Fold the wet mixture through the dry ingredients until evenly combined. Transfer to the tin.
Bake for 45-50 minutes, until golden and a skewer inserted into the centre comes out with a few moist crumbs.