In a large bowl mix the dry ingredients: flour, salt, baking powder, sugar, and lemon zest, and set aside.
In a separate bowl, beat the butter and sugar with a whisk until a creamy texture is obtained.
Add the egg and beat again until it is fully incorporated into the butter and sugar mixture.
Gradually add the dry ingredients (flour mixture)and mix well with a spatula or the flat beater of the KitchenAid to form a smooth short pastry dough. Mix carefully to avoid aerating the dough.
Divide the dough in two parts and set aside in cling film, chill for at least two hours into the fridge.
Prepare the baking pan with release spray and flour or baking paper.
Preheat the oven to 170º Celsius (347º Fahrenheit).
Roll out half of the dough on a floured surface , the line the baking pan with it, covering the sides of the pan completely.
Fill the bottom crust generously with a layer of jam, raspberry jam if possible, using a pastry bag or a spoon.
Roll out the remaining dough, the other half of the dough, and cut it into strips or use a cookie cutter to make shapes (such as stars or crescent moons).
Place the strips or shapes on top of the jam to form the traditional decoration of a Linzer cake.
You can brush the top of the tort with egg wash, this step is completly optional, just helps with the delicate, golden finish.
Bake for 30-40 minutes until the edges are golden brown.
Let the cake cool on a wire rack in a cool place, the carefully unmold once fully cooled to avoid breaking the crust.
Serve on a pie plate sprinkled with icing sugar or brown sugar and enjoy your Linzer torte!