In a bowl, combine almond flour, coconut flour, melted butter, egg, and salt. Stir until well combined.
Press the dough into the bottom of a greased pie dish or a tart pan, spreading it evenly to form a crust.
Bake the crust for 8-10 minutes, or until lightly golden. Remove from the oven and set aside.
For the Filling:
In a large pan, heat olive oil over medium heat. Add the onion and garlic, cooking until softened and fragrant (about 3-4 minutes).
Add the chopped spinach to the pan, cooking until wilted and the moisture evaporates (about 5-7 minutes).
Remove the pan from the heat and let the spinach mixture cool slightly.
In a bowl, combine the cooked spinach, feta cheese, ricotta cheese, Parmesan cheese, beaten eggs, dill, parsley, salt, and black pepper. Mix until well combined.
Assembling the Pie:
Pour the spinach mixture over the pre-baked crust, spreading it evenly.
Return the pie to the oven and bake for an additional 25-30 minutes, or until the filling is set and golden brown on top.
Let the pie cool slightly before slicing and serving.