Preheat oven to 350 degrees.
In a large mixing bowl combine the chopped onion, eggs, cottage cheese, grated cheese and pepper. Mix with a spatula until blended. Set aside.
Wilt the spinach. Remove the spinach to a strainer. Drain the spinach well then press it with paper towels until you remove as much moisture as you can. Rough chop the spinach and add it to the cheese and egg mixture. Fold with the spatula until combined.
Spray a tart pan. Place the mixture into the tart pans (with removable bottom). Press the spinach and cheese mixture into the tart pans smoothing to level the top.
Bake for 35-40 minutes or until just set in the center and lightly browned on the edges.
Remove from the tart pan. Cut into squares.
Serve and enjoy!