Preheat the oven to 325 degrees F (160 degrees C).
Pour Butter (125 gram), Egg (2), Milk (2 tablespoon), Caster Sugar (70 gram), Vanilla Extract (1 teaspoon), Lemon Juice (1 tablespoon), Lemon (to taste), Self-Rising Flour (125 gram) into a large bowl.
Whisk the ingredients in the large bowl at low speed until just combined, about 30 seconds. Then gently fold well the mixtures with a rubber spatula.
Fill the cases or cupcake liners to 2/3 full and bake in the middle rack of the oven for about 25-30 minutes or test with a skewer inserted into the cake. If it's ready it should come out clean.
Meanwhile, start making the lemon syrup. Boil the Lemon Juice (2 tablespoon) and Caster Sugar (3 tablespoon) until the sugar is dissolved at low heat.
When the cakes are finished, let them cool for about 5 minutes, then remove the cake from the cases and poke each a few times with the skewer. Then brush the warm lemon syrup generously onto the cakes. Leave the cakes to cool before serving.