Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe ramekin or baking dish.
In a non-stick skillet over medium heat, add the olive oil and sauté the diced yellow onion and minced garlic until translucent and fragrant.
Add the ground turkey to the skillet, seasoning with sea salt, black pepper, and dried oregano. Cook until the turkey is browned and cooked through.
Stir in the fresh spinach and cook just until wilted, then remove the skillet from the heat to cool slightly.
In a small bowl, whisk the egg whites and then stir them into the turkey and spinach mixture along with the crumbled feta cheese.
Lay one sheet of phyllo dough into the baking dish, allowing the edges to hang over. Lightly brush or spray with a tiny amount of oil, then layer the second sheet on top in the opposite direction.
Spoon the turkey and spinach filling into the center of the phyllo dough.
Fold the overhanging edges of the phyllo dough over the top of the filling to create a rustic, enclosed pie.
Bake for 20-25 minutes, or until the phyllo is deeply golden brown and the filling is set.
Let the pie rest for 5 minutes before serving to allow the layers to crisp up further.