Preheat your oven to 375°F and lightly grease a small oven-safe baking dish with a drop of olive oil.
Place the thawed spinach in a clean kitchen towel and squeeze firmly until all excess liquid is removed to ensure a crisp crust.
In a medium bowl, whisk together the egg whites, whole egg, chopped dill, sliced green onion, sea salt, black pepper, and garlic powder.
Stir the squeezed spinach and crumbled feta cheese into the egg mixture until the ingredients are evenly distributed.
Lay one sheet of phyllo dough into the baking dish, allowing the edges to hang over, and lightly brush with a small amount of olive oil.
Place the second sheet of phyllo on top, rotating it slightly to cover more area, and brush again with the remaining olive oil.
Pour the spinach and egg mixture into the center of the phyllo and fold the overhanging edges back toward the center to create a rustic border.
Bake for 30 to 35 minutes until the egg filling is completely set and the phyllo pastry is golden and flaky.