Preheat oven to 180 C. Grease a loaf tin and line with parchment paper.
Beat margarine and sugar, on medium speed, until creamy. Add the eggs and lemon zest and mix for 3 to 4 minutes, until well incorporated. Sift the flour, baking powder and milk into the egg mixture. Mix until combined.
Pour the mixture into the prepared tin and bake for 35-40 minutes or until a toothpick, inserted in the center, comes out clean.
To make the syrup combine the sugar and lemon juice in a saucepan. Place over low heat and stir until the sugar dissolves.
When the cake is cooked prick all over with a toothpick. Pour the syrup all over the cake and leave to absorb. Leave to cool and serve.