For the drizzle topping
Heat oven to 180C/fan 160C/gas 4. Beat together 225g softened unsalted butter and 225g caster sugar until pale and creamy, then add 4 eggs, one at a time, slowly mixing through. Sift in 225g flour, then add the finely grated zest of 1 lemon and mix until well combined. Line a loaf tin (8 x 21cm) with greaseproof paper, then spoon in the mixture and level the top with a spoon.
Bake for 45-50 mins until a thin skewer inserted into the centre of the cake comes out clean. While the cake is cooling in its tin, mix together the juice of 1 1/2 lemons and 85g caster sugar to make the drizzle. Prick the warm cake all over with a skewer or fork, then pour over the drizzle – the juice will sink in and the sugar will form a lovely, crisp topping. Leave in the tin until completely cool, then remove and serve. Will keep in an airtight container for 3-4 days, or freeze for up to 1 month.