Preheat oven to 350°. Spray a 13x9-inch baking dish with cooking spray.
In a large Dutch oven, bring squash, onion, and water to cover to a boil over medium-high heat. Cook until just tender, about 8 minutes; drain well.
In a large bowl, stir together sour cream, mayonnaise, eggs, green onion, and flour. Stir in cheese, bell pepper, salt, and pepper. Gently stir in squash mixture. Pour into prepared pan.
In a medium bowl, stir together cracker crumbs and melted butter; sprinkle onto casserole.
Bake until set, 35 to 40 minutes.
Notes
Kitchen Tip: Squash Casserole can be prepared through step 3 and refrigerated overnight. Let it stand at room temperature for 30 minutes before topping with cracker crumbs and baking as directed.
Recipe by Paula Deen Magazine at https://pauladeenmagazine.com/2-squash-casserole-recipe/