Start by getting everything ready. Heat your oven to 180°C (350°F). Grease your cake tin well and line the base with baking paper so the cake doesn’t stick.
In a large bowl, beat the butter and sugar together until the mixture looks pale and fluffy. Take your time here, as this step helps make the cake light and soft.
Add the eggs one at a time, beating well after each one. This helps keep the batter smooth and prevents it from curdling.
In a separate bowl, sift together the flour, baking powder, and salt to remove any lumps and evenly mix the dry ingredients.
Gradually add the dry ingredients to the butter mixture, folding gently so you don’t knock out the air. Stir in the lemon zest, lemon juice, and milk if you’re using it, mixing just until everything comes together.
Pour the batter into the prepared tin and smooth the top. Bake for 35 to 40 minutes, or until a skewer inserted into the center comes out clean. Let the cake rest in the tin for about 10 minutes, then turn it out onto a wire rack and allow it to cool completely.