Preheat your oven to 375°F (190°C).
In a non-stick skillet, sauté the finely diced yellow onion and minced garlic in olive oil over medium heat until translucent and fragrant.
Add the fresh spinach to the skillet and cook until fully wilted; once cooled slightly, place the spinach in a clean kitchen towel and squeeze out all excess moisture to prevent a soggy pie.
In a blender, pulse the low-fat cottage cheese until completely smooth, then transfer to a mixing bowl and whisk in the liquid egg whites, sea salt, black pepper, and ground nutmeg.
Fold the squeezed spinach, crumbled feta cheese, and chopped fresh dill into the egg mixture until well combined.
Lightly coat a small oven-safe baking dish with oil and layer two sheets of phyllo dough in the bottom, allowing the edges to hang over the sides of the dish.
Pour the spinach and egg protein mixture into the dish, spreading it evenly.
Fold the overhanging phyllo edges back over the filling and top with the remaining two sheets of phyllo dough, crinkling them slightly on top to create a rustic, crunchy texture.
Bake for 30-35 minutes until the filling is firmly set and the pastry is crisp and golden brown.