Heat oil in a pan over medium heat. Sautee onions until translucent. Add frozen spinach and turn off heat. Set aside.
In mixing bowl, beat eggs . Add cottage cheese, feta, herbs, and lemon zest. Stir. Add spinach and onion mixture. Optional: place filling mixture in food processor and pulse until desired consistency.Optional: if preparing filling ahead of time, place covered in fridge until ready to use.
Pour filling into pie crust. Bake at 375 for 35 minutes. Enjoy!