1.Preheat your oven to 180°C/Gas 4. Line a 20cm x 20cm square baking tin with parchment paper.
2. Using an electric whisk, beat the butter and caster sugar together until pale, light and fluffy. Add the eggs and mix again. Add the flour, baking powder, lemon zest, lemon curd and milk and mix with a wooden spoon until all the ingredients are thoroughly combined. Pour the mixture into the prepared tin and bake for 25 to 30 minutes or until a skewer comes out clean.
3. Mix the granulated sugar and lemon juice together and pour over the hot cake. Leave to cool in the tin. You can then eat the cake just as it is, or for a fancy finish try making this feather icing.
4. Mix the icing sugar with just enough of the water to give a runny, but not watery, icing. Take a small amount of icing and place it in a separate bowl. Add a few drops of the food colouring to this icing until you have the desired colour. Spoon this not a disposable icing bag.
5. Remove the cake from the tin and peel off the parchment paper. Sit the cake on a wire rack over a baking tray. Spread the white icing over the cake. Using the icing bag, pipe lines of the coloured icing across the width of the cake. Using a cocktail stick, drag through the lines at right angles to create a feathered effect. Leave to set before cutting into 12 slices.
Photography by Issy Crocker