Step 1

Preheat oven to 350 degrees F. Coat a 9-by-13-inch baking dish (or similar-size 3-quart baking dish) with cooking spray.

Step 2

Place squash on a clean kitchen towel, gather up the edges and squeeze out excess moisture.

Step 3

Heat butter in a large skillet over medium heat. Add onion and cook, stirring occasionally, until golden brown, 5 to 8 minutes. Add the squash and a pinch of salt; cook until very soft and dry; about 4 minutes more.

Step 4

Transfer the squash mixture to a large bowl. Add corn, cottage cheese, feta, bell pepper, dill, flour, baking powder, pepper and the remaining 1/4 teaspoon salt and stir until well combined. Stir in eggs. Pour the mixture into the prepared baking dish.

Step 5

Bake the casserole until the center is set and the edges are lightly browned, about 40 minutes. Let stand 10 minutes before serving.