Summer Squash Casserole

3 pounds yellow or zucchini squash

1 medium onion, diced

2 cups coarsely crushed Ritz or soda crackers, DIVIDED

2 tablespoons butter or margarine, DIVIDED

Salt and pepper, to taste

Preheat oven to 350 degrees. Cut squash into 1/2 inch slices. Place in large saucepan with onion. Add enough water to cover; bring to simmer. Cover and cook until squash is tender, 10 to 15 minutes. Drain and mash slightly in a colander, pressing to remove as much liquid as possible. Transfer to a large bowl. Add 1/2 cup of the crackers and 1 tablespoon butter to squash. Season with salt and pepper and mix well. Transfer to an 8 inch square baking dish. Sprinkle with remaining crumbs; dot with 1 tablespoons butter. Bake until golden, 20 to 30 minutes.