Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe baking dish with the olive oil.
Place the thawed frozen spinach in a clean kitchen towel and squeeze vigorously to remove every drop of excess moisture.
In a medium mixing bowl, whisk together the whole egg, liquid egg whites, and nonfat Greek yogurt until smooth.
Fold in the squeezed dry spinach, crumbled feta cheese, chopped green onions, and fresh dill.
Season the mixture with sea salt and black pepper, stirring to ensure the feta is evenly distributed.
Lay one sheet of phyllo dough into the prepared dish, allowing the edges to hang over, and lightly brush with a tiny amount of water or oil spray.
Layer the second sheet of phyllo on top, rotating it slightly to cover more surface area.
Pour the spinach and egg mixture into the center of the phyllo-lined dish.
Fold the overhanging edges of the phyllo dough back toward the center to create a rustic crust around the filling.
Bake for 30 to 35 minutes until the egg filling is firm and the phyllo is deeply golden and crisp.