Preheat oven to 375°
In a small bowl mix spinach, diced onion, ricotta cheese, parmesan cheese, eggs, dill, panko, and black pepper. (It's best to use a fork for mixing.)
Break the feta cheese into very small pieces and fold it into the spinach mixture.
Transfer spinach to a baking dish that has been sprayed with non-stick cooking spray.
Bake for 30 minutes covered.
Remove cover and bake for another 5-7 minutes or until the edges begin to turn brown and pull away from the sides of the baking dish.
Let it cool for 5 minutes before serving.