Preheat the oven to 180°C.
In a bowl, whisk room-temperature butter with fine caster sugar (not icing sugar) until slightly creamy.
Add the eggs one at a time, whisking well after each addition.
Pour in the milk, lemon juice, and vanilla extract, then whisk again.
Gradually add sifted flour, baking powder, and bicarbonate of soda. Mix thoroughly.
Stir in the poppy seeds and lemon zest.
Line a cake tin (22-25 cm) with baking paper:
For a higher cake, use a 22 cm tin.
For a medium-sized cake with faster cooking, use a 25 cm tin.
Pour the batter into the prepared tin.
Bake for 55 minutes or until a knife inserted into the cake comes out clean.
Remove from the oven and allow the cake to cool slightly before unmolding.