Start by heating your oven to 160C. Grease a loaf tin and line it with parchment paper to ensure an easy release of the cake once baked.
In a sizable mixing bowl, combine the unsalted butter, caster sugar, eggs, self-raising flour, and lemon zest. Beat these ingredients together until the mixture is creamy and homogenous.
Transfer this batter into your prepared tin, smoothing the top to create an even layer. Bake in the preheated oven for 40 to 50 minutes, or until a skewer inserted into the center of the cake comes out clean, indicating that it is thoroughly cooked.