Why Does My Lemon Polenta Cake Sink?

Our answer

Nigella's Lemon Polenta Cake (from KITCHEN) is made with a combination of polenta and ground almonds (almond meal), making it gluten free. Unfortunately as it is gluten free it is likely to sink slightly as it cools. In regular cakes the proteins in the gluten set as the cake bakes, keeping the shape of the cake. But gluten-free cakes lack the same structure so generally sink slightly as they cool. You can see that the cake in the photograph has sunk slightly in the centre.

If the cake is completely collapsing in the centre it could be that the combination of baking powder plus beating in too much air has caused the cake to rise a lot during baking, causing a more dramatic sinking as the cake cools. Once the butter and sugar have been creamed together you don't need to beat the other ingredients in too vigorously. Or you could, as Nigella suggests in the introduction, leave out the baking powder and beat vigorously while mixing the cake batter. The other possibility is that the cake is not quite fully baked in the centre. Look for the sides of the cake shrinking away from the pan and a cake tester inserted into the centre should come out clean or just with the odd cake crumb on it.