Preheat your oven to 375°F (190°C).
Place the thawed spinach in a clean kitchen towel and squeeze forcefully until all excess moisture is removed.
Heat the olive oil in a small skillet over medium heat and sauté the sliced green onions until softened.
In a medium mixing bowl, whisk together the egg whites, sea salt, black pepper, nutmeg, and chopped fresh dill.
Stir the dried spinach, sautéed onions, and crumbled feta cheese into the egg white mixture until well combined.
Lightly coat a small oven-safe baking dish with oil spray and lay one sheet of phyllo dough inside, allowing the edges to hang over.
Place the second sheet of phyllo dough crosswise over the first.
Pour the spinach and egg mixture into the center of the dish.
Fold the overhanging edges of the phyllo dough over the top of the filling to partially cover it.
Bake for 30 to 35 minutes until the filling is firm and the pastry has turned a deep golden brown.