Add almond flour, xanthan gum, coconut flour and erythritol into a mixing bowl. Whisk until well combined. Add the butter and rub it into the dry ingredients until it resembles breadcrumbs.
Add remaining crust ingredients and mix to form a dough.
Flatten the dough into a disk shape, cover with plastic wrap, and chill in the fridge for 30 minutes.
While the dough is chilling, prepare the filling by peeling and dicing the zucchini.
Heat a large pot and melt the butter, allowing it to melt and turn slightly brown. Add the diced zucchini, reduce the heat, and stir for 5 minutes.
Add all remaining filling ingredients except for the arrowroot powder. Stir through and cook on low heat, stirring occasionally for 10 minutes or until the zucchini is tender.
Taste the zucchini and adjust the flavors by adding extra lemon juice, cinnamon or sweetener to suit your taste.
In a small bowl, mix the arrowroot powder with 1 tablespoon of cold water, stir to form a slurry.
Gently stir through the arrowroot mixture and cook until the filling mixture thickens.
Remove from heat and allow to cool completely in the fridge before filling the pie crust.
Preheat the oven to 320 degrees F / 160 C. Lightly spray a 9 inch pie dish with spray oil.
Cut the chilled dough in half. Place one half of the dough, covered, back into the fridge and the other half in between 2 sheets of baking paper.
Roll the dough out thinly to fit a 9 inch pie dish.
Remove the top sheet of paper and line the prepared pie dish with dough, trimming the edges and using a fork to pierce the base.
Cook in the oven for 8-10 minutes, making sure not to overcook and brown the edges.
Remove and allow it to cool before filling with cold pie filling and coating the edges with either water or egg wash.
Roll the remaining dough in between 2 sheets of baking paper, removing the top sheet and laying the dough on top to cover the pie filling.
Trim the edges and pierce the top with a knife. Optional: Brush the top of the pie with egg wash.
Cook in the oven for 10-15 minutes or until lightly golden brown. When cooked through remove from the oven and allow to cool before serving.