Prep. Preheat the oven to 350 degrees Fahrenheit and lightly grease a 2-quart casserole dish.
Saute cabbage. Chop the cabbage into coarse pieces. In a large nonstick pan, melt the butter.
Add onion. Add the cabbage and onion, cooking for 8 to 10 minutes while stirring frequently, until it starts to cook down. At the end of cooking, season the mixture with salt and pepper according to your taste.
Transfer the cooked cabbage mixture into the prepared baking dish. Set aside.
Make the creamy sauce. Combine the mushroom soup and mayonnaise in a small bowl, stirring well. Spread this mixture evenly over the cabbage.
Mix the topping ingredients. In another bowl, mix the melted butter, cheese, and cracker crumbs. Sprinkle this mixture over the casserole.
Bake in the oven. Bake for 30 minutes or until the topping turns golden brown. Let cool a bit and enjoy!