In a food processor, sift your flour, salt and powdered sugar. Add cold cubes of butter. Pulse until the mixture is like a coarse sand, with a few bigger chunks of butter. Add 3 tablespoons of ice cold water and pulse until the dough starts clumping together, not more than that. If it doesn't start coming together, then add another tablespoon of ice cold water. When it's done, it should still be crumbly - that's fine, because we want to combine it together with our hands.
Transfer the dough onto a lightly flour surface and using your hands just combine it until it forms a homogenous dough. Form into a disk, wrap in cling film and leave it in the fridge for at least an hour or up to three days.
Preheat your oven to 180°C (350°F) and line a baking sheet with baking paper.
In a medium sized bowl, combine sugar, cardamom, cinnamon and cornstarch with the whisk. Add sliced nectarines and blackberries and combine everything with a wooden spoon or a spatula. Set aside.
Once your dough is chilled, leave it on the counter for a few minutes, then roll it in a 4-5 mm thick (⅛ inch) circle. Strain your fruit to get rid of the liquid, but save it. Place the nectarines and blackberries on the dough, making sure to leave a couple of centimeters form the edge. You can shape it slice by slice, or just spoon eveything without a pattern.
Fold the edges over the filling and press slightly to seal them together. Brush the edges with beaten egg and sprinkle with demerara sugar.
Melt the butter and combine with couple of tablespoons of that liquid you saved from the fruit. Pour over the fruit. Put in the oven and bake for about 35-40 minutes, or until the edges are golden and fruit caramelised.
Leave it on the cooling rack to cool for 5-10 minutes, then serve warm with a scoop of vanilla ice cream. :)
Notes
If you don't have a food processor, you can make the dough with your hands. The recipe for the pie crust is adapted from Cupcake Jemma and you can check her video here - where she makes it with her hands. :)
If you still don’t own one, I advise you to buy a kitchen scale – they’re cheap and easy to use, and always guarantee the same results in baking!