In a mixing bowl, add All-Purpose Flour (1 1/2 cup), Powdered Confectioners Sugar (1/2 cup), and Butter (150 gram). Mix together.
Press dough into the bottom of a lightly greased 18 by 28-centimeter pan lined with parchment paper.
Bake at 180 degrees C (350 degrees F) for 15 minutes.
In a mixing bowl, add Sweetened Condensed Milk (400 gram) and Egg (1). Beat together until smooth. Add Self-Rising Flour (2 tablespoon) and Lemon Juice (1/2 cup). Mix again.
Pour the lemon mixture over the top of the crust.
Bake for another 30 minutes, or until the top has set.
Allow lemon slice to cool for 10 minutes.
Place lemon slice in fridge for 1 hour to cool.
Slice, serve, and enjoy!