Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe baking dish.
Thaw the frozen spinach and squeeze it very dry using a kitchen towel to remove all excess moisture.
In a medium mixing bowl, whisk together the liquid egg whites, Greek yogurt, garlic powder, onion powder, sea salt, and black pepper until smooth.
Stir in the squeezed dry spinach, crumbled feta cheese, and chopped fresh dill until well combined.
Lay one sheet of phyllo dough on a clean surface and lightly brush with a tiny amount of olive oil. Stack the remaining two sheets on top, brushing each lightly.
Carefully press the phyllo stack into the prepared baking dish, allowing the excess dough to hang over the sides.
Pour the spinach and egg mixture into the center of the dough.
Gently fold the overhanging phyllo edges back over the filling towards the center, leaving a small opening in the middle.
Bake for 25 to 30 minutes, or until the phyllo is deeply golden brown and the egg filling is firm and set.
Allow the pie to cool for 5 minutes before slicing and serving.