Prepare the pastry: place the flour, sugar and salt into the bowl of a food processor and pulse several time to combine.
Next, add the diced cold butter to the flour mixture and continue to pulse until the butter resembles small pea sized pieces.
While the food processor is running pour in cold water until a dough begins to form.
Transfer the dough to a bench and bring the dough together, divide in half and form 2 discs.
Wrap in plastic wrap and chill in the fridge for at least an hour.
Meanwhile prepare the filling by mixing the sugar, lemon juice, zest, cornstarch, almond extract and frozen cherries.
Stir continuously over a low heat until the mixture has thickened, this may take between 8-10 minutes.
Remove from the heat and cool to room temperature.
Once the dough has chilled remove one disc and roll it into a circle approximately ⅛ inch thick on a lightly floured bench to fit a 9 inch pie dish.
Line the pie dish with pastry and fill with the cooled cherry filling. Arrange the diced butter pieces over the filling.
Place the pie in the fridge while preparing the top layer of pastry.
Roll the remaining pastry approximately ⅛ inch thick and large enough to cover the pie dish.
Cut the pastry into 10 strips approximately 1 inch wide, these will be used to top the pie.
Whisk the egg in a small bowl and brush the edges of the pastry.
Lay 6 strips parallel over the top of the pie, leaving a small space between each strip.
Fold back every second strip and lay the remaining 4 strips in a lattice design over the pie.
Weave the strips over and under each other to cover the pie filling.
Trim the edges of the pastry with a knife.
Using your fingers, crimp the pastry to seal the edges.
Chill the pie for another 30 minutes.
Preheat the oven to 350 degrees F / 180 C.
Brush the top of the pie with the whisked egg and finish off with a sprinkle of sugar.
Bake on the middle shelf of the oven for 40-50 minutes.
Remove form the oven and allow to cool for 2 hours before serving and enjoying.