Start by preheat oven to 350°F/180°C and greasing a baking dish.
We’ll start with the dough for the crust. In a large mixing bowl, mix together the butter and powdered sugar. Follow that by mixing in the flour and salt until the dough is combined.
Press your new dough into the bottom of the baking dish. Ensure it’s covered the base and inside of the dish, and is spread evenly.
Bake the dough for 10 minutes.
Remove the dish from the oven (but leave the oven on!) and set to one side.
Now onto the filling. In a new mixing bowl, stir the sugar and lemon zest until combined. Then add in the flour, baking powder, eggs and lemon juice. Combine thoroughly until the sugar has dissolved.
Pour the mixture over the baked crust and place baking dish back in the oven. Bake at same temperature until the lemon filling has set, usually about 20 minutes.
Remove the baking dish from the oven. Sprinkle powdered sugar over the dish and leave to one side to cool and set.
Once set, cut into squares and serve.