Preheat your oven to 180°C (350°F).
In a large mixing bowl, combine the spinach, feta cheese, onion, garlic, eggs, olive oil, dill, parsley, salt, and pepper. Mix well.
Brush a baking dish with melted butter. Layer half of the phyllo dough sheets, brushing each sheet with butter.
Spread the spinach mixture evenly over the phyllo dough.
Layer the remaining phyllo dough sheets on top, brushing each sheet with butter.
Bake in the preheated oven for 45 minutes, or until the top is golden brown and crispy.
Let it cool for a few minutes before slicing and serving.