1

Preheat the oven to 170°C, fan 150°C, gas mark 3½ and line a 900g loaf tin with baking paper.

2

Pare off a few long strips of lemon zest using a zester (or use a vegetable peeler to remove 2 strips of outer peel, then cut these into fine shreds), and set aside, covered, to finish the cake. Finely grate the rest of the zest from both lemons, and squeeze the juice from both.

3

In a large mixing bowl, beat the grated lemon zest, low-fat spread and caster sugar together using a hand-held electric whisk until pale and creamy. Beat in the eggs, one at a time, adding a spoonful of the flour with each egg. Add the rest of the flour, along with the baking powder, polenta and half the lemon juice. Mix for 1 minute until you have a smooth batter.

4

Pour the batter into the prepared tin, smooth the top with a spatula and bake for 40-60 minutes, or until a skewer inserted into the centre of the cake comes out clean.

5

Mix the remaining lemon juice with the Demerara sugar in a small jug. Pour over the top of the cake while it is still warm, then set aside to cool in the tin.

6

When the cake is cool, turn it out onto a serving plate and remove the baking paper. Top with the reserved pared lemon zest and cut into slices to serve.