Preheat the oven to 350°F (175°C).
Sauté fresh spinach in a skillet until wilted, then drain and squeeze out all excess moisture. If using frozen spinach, thaw and fully squeeze.
For the crust, combine almond flour, melted butter, egg, and salt until a dough forms.
Roll the dough between parchment sheets, then press into a pie dish. Pre-bake for 10 minutes.
Sauté onion and garlic in butter until soft and fragrant.
In a bowl, whisk together eggs, heavy cream, and cream cheese until smooth.
Add sautéed onion, garlic, feta, mozzarella, dill, salt, and pepper. Fold in the spinach.
Pour the filling into the pre-baked crust and spread evenly.
Optional: Sprinkle extra mozzarella on top.
Bake for 25–30 minutes, or until the top is lightly golden and the filling is set.
Let cool for 5–10 minutes before slicing and serving.