Preheat your oven to 160°C (320°F) for a conventional oven. Grease a 900 g loaf tin or 20 cm round cake tin and line it with baking parchment. Preparing the tin properly helps prevent sticking and makes it easier to remove the finished cake without damaging its golden crust.

Place the softened butter and caster sugar in a large mixing bowl. Beat with an electric mixer for approximately 3–5 minutes until the mixture becomes pale, light, and fluffy. This step incorporates air into the batter, helping the cake develop a tender texture while retaining the slightly firm structure expected from a traditional Madeira cake.

Add the eggs one at a time, beating well after each addition. If the mixture begins to look curdled, add a spoonful of the measured flour and continue mixing gently. Stir in the vanilla extract and finely grated lemon zest, distributing the flavor evenly throughout the batter.

Sift the self-raising flour and plain flour together into the mixing bowl. Using a spatula or a low mixer setting, fold the flour into the butter mixture until just combined. Avoid overmixing, as excessive mixing can make the finished cake tough. If the batter seems unusually stiff, add the milk gradually until it drops from the spoon with a thick consistency.

Transfer the batter into the prepared tin and level the surface gently. Sprinkle the optional caster sugar over the top for a delicate sugary crust. Bake for approximately 50–60 minutes, checking near the end of the baking time. The cake is ready when it is golden, a skewer inserted into the center comes out clean, and the middle springs back lightly when touched.

Leave the cake in its tin for around 10–15 minutes before carefully transferring it to a wire rack. Allow it to cool completely before slicing so the crumb can set properly. Serve thick slices with tea or coffee, or add fresh berries and a little cream when you want a more indulgent dessert.