Preheat the oven to 160 °C. Line the bottom and sides of a 23 cm spring form tin with baking paper.

For the glazed lemon topping, place the lemon slices in a saucepan and cover with cold water. Bring to the boil and simmer for 30 minutes. Drain and add the sugar and water. Boil for 30 minutes or until a syrupy consistency.

Lift the lemon slices out of the syrup and allow to cool on baking paper.

Reduce the leftover lemon syrup until halved and reserve for later.

For the cake, cream the butter and sugar until pale and creamy.

Combine the almonds, polenta, and baking powder. While whisking, add the dry ingredients, alternating with the eggs.

Whisk in the lemon zest and spoon into the prepared tin. Bake for 40 minutes. The cake may seem unstable but is ready when a cake tester inserted into the center of the cake comes out clean. Remove from the oven. Place on a wire rack to cool in the tin.

For the syrup, bring the lemon juice and icing sugar to a boil. Prick the top of the cake with a cake tester and pour the warm syrup over the cake. Leave to cool before taking it out of its tin. Serve the cake topped with glazed lemons, extra lemon syrup, and double cream.