Remove the seeds and cut out a wide slit in each pepper lengthwise.
Preheat the oven to 375 degrees. Spray a rimmed baking sheet with cooking spray.
Combine the spinach, cottage cheese, pesto, bread crumbs, Parmesan cheese and black pepper in a medium bowl until well mixed. Place the peppers on the baking sheet. Fill each with 1 to 2 tablespoons of the spinach mixture, depending on the size of the peppers. The top of the filling should extend a bit above the edge of the pepper. Bake for 35 minutes or until the top of the filling is slightly browned and crisp.
Sprinkle with additional Parmesan, if desired, before serving.