I have made the lovely Lemon Polenta cake many times but it always sinks in the middle! I get round this by putting raspberries in the “dip” and serving as a dessert, but is there any way to prevent it? I also substitute half the lemon juice in the syrup with limoncello - delicious!
Nigella's Lemon Polenta Cake (from KITCHEN) is a gluten-free cake made with a combination of ground almonds (almond meal or almond flour) and polenta (or cornmeal). As the cake doesn't contain any gluten it will tend to sink slightly in the centre as it cools and if you look carefully at the photo you will see there is a slight dip at the tip of the slice of cake.
If the cake is sinking dramatically then it may need a couple of minutes longer in the oven to help to set the centre slightly more. A cake tester inserted into the centre should come out clean or just with a couple of crumbs of cake on it, and not wet cake mixture. Also be careful not to beat too much air into the mixture when creaming the butter and sugar and then when adding the other ingredients. Air bubbles in the batter will expand in the heat of the oven but once the cake is removed the air bubbles contract as they cool and as there is no gluten in the cake it has a weaker structure, meaning that the cake will sink as it cools. Beat the butter and sugar just until pale and the sugar has mostly dissolved then beat in the eggs, alternating with the dry ingredients, until just mixed.