1. Preheat the oven to 180ºC/ fan 160°C/gas 4. Grease and  line a 20x30cm baking tray with baking paper.
2. Using an electric hand mixer, cream the low-fat spread and 180g sugar together in a mixingbowl until light and fluffy. Beat in the eggs, then fold in the ground almonds, mashed potato, zest of 3 lemons and baking powder.
3. Spoon the mixture into the prepared baking tray, then bake for 40–45 min until lightly golden and firm to the touch. Cool in the tin for 5 min, then turn out on to a wire rack to cool completely.
4. Meanwhile, make the lemon drizzle: put the sugar and lemon zest and juice in a small pan. Cook, stirring, over a low heat until the sugar dissolves. Continue cooking and stirring for a further 3 min or until slightly thickened.
5. Prick the top of the cooled cake all over with a skewer. Drizzle over the syrup, then set aside for 1 hr.
6. To serve, lightly dust the cake with the icing sugar, decorate with extra lemon zest, then cut into 20 squares.

TIP 2  medium baking potatoes should be about right for this recipe. Scrub and prick them all over, then microwave or steam until tender before mashing.