Make sure the butter and water you are using is cold.
Whisk the egg, and set aside.
Finely dice the butter, add to the gluten-free flour and rub with your fingertips until you have fine breadcrumbs. Make a well in the center and add the egg and a pinch of salt.
Bring the mix together until it forms a ball. Knead with the palm of your hand until smooth, wrap in cling film and rest in the fridge for at least 30 minutes. The pastry can keep for approximately three days in the fridge or you can freeze it for use at a later date.
To line and blind bake a tart case:
Preheat the oven to 180'C.
Roll the pastry out between 2 sheets of baking paper to 5mm thick. Transfer the pastry to the tart case and trim the edges. Line with baking parchment and cover with baking beans. Transfer to the oven and blind bake for 20 minutes until golden brown.
Once cooked, check the pastry case for any small cracks and fill with the left over pastry if necessary.
«If your tart shells are too crumbly, you can add body to the dough by adding 20g of ground flax seeds or psyllium husk and about 2 tablespoons of water. If dairy is also an issue, the unsalted butter can be substituted with coconut oil or butter»