Preheat your oven to 375°F (190°C) and lightly coat a small oven-safe baking dish with a tiny bit of olive oil.
Thaw the frozen spinach completely and place it in a clean kitchen towel, squeezing forcefully until all excess moisture is removed and the spinach is dry.
Finely chop the green onions and fresh dill.
In a medium mixing bowl, whisk together the liquid egg whites, whole egg, Greek yogurt, sea salt, black pepper, and garlic powder until smooth.
Stir the squeezed spinach, crumbled feta cheese, green onions, and dill into the egg mixture until well combined.
Lay one sheet of phyllo dough into the baking dish, allowing the edges to hang over, and lightly brush with a fraction of the olive oil.
Place the second sheet of phyllo on top, rotating it slightly to cover more surface area.
Pour the spinach and egg filling into the center of the phyllo sheets.
Gently fold the overhanging edges of the phyllo dough over the top of the filling, leaving the center slightly exposed for a rustic look.
Bake for 30 to 35 minutes, or until the egg filling is set and the phyllo pastry is deeply golden brown and flaky.
Allow the pie to cool for 5 minutes before slicing to ensure the filling stays intact.