Put the flour and cold butter in a mixer until you get a sandy mixture.
Add sugar, eggs, and grated lemon peel.
Work the ingredients together with the mixer and when they are mix enough transfer them to a flat workspace and work them with your hands until it's a compact dough.
Wrap the dough in plastic wrap and let it rest in the fridge for at least a ½ hr.
After, roll out the dough until reaches ½ cm (0.25 inches) of thickness.
Then put the dough in the tart pan of 24-25 cm (9 inches) in diameter, cutting the excess of dough over the edges of the pan.
Gelo di Melone
Pass watermelon pulp through the food mill to obtain 1 liter of juice.
Filter it to remove pulp and seeds.
Pour the juice into a saucepan with the brown sugar, cornstarch, and cinnamon stick.
Heat the mixture, stirring constantly until it becomes thick.
Remove the mixture from the stove and take out the cinnamon stick.
Pour the liquid Melon jelly into a round pan that has 24 cm (9 inches) in diameter, let it cool down, and solidify.
Assembling
When the melon jelly is solidified carefully remove it from the mold and place it on the dough in the other pan.
Then cover the WaterMelon tart with strips ( 1cm in width -0.4 inches) ) of the leftover shortcrust.
Bake it for 35-45 minutes at 180°C (356 °F).
Remove from the oven and let it cool completely down, sprinkle with powdered sugar and grounded pistachios.