Anything bright and zingy is particularly welcome in January, even more so when it’s in the form of cake. The marzipan gets blitzed into the butter for a plush-textured loaf cake, and comes together in minutes thanks to simply putting everything in a food processor. Add the sugar and orange and lemon zest, give the mix a quick pulse, then add the eggs and pulse again. To make the icing, mix two tablespoons of orange juice with two tablespoons of lemon juice in a small bowl. Remove the cake from its tin, then pour over the icing.