Preheat oven to 350℉.
Chop cabbage into bite sized pieces.
Cut onion in half and slice thinly.
Toss together cabbage and onion in a large mixing bowl.
Transfer cabbage and onion into an oven safe casserole dish.
Sprinkle with salt.
Drizzle with ½ stick of melted butter.
In a a small mixing bowl stir together mayonnaise, cream of celery soup, and pepper.
Drop soup mixture on top of cabbage and onions. Use the back of a spoon to spread the soup mixture out evenly to the edges of the pan.
In a large mixing bowl stir together the crushed crackers, (I used Ritz crackers), shredded cheddar cheese and 1 stick melted butter.
Spread the cheese/cracker mixture out over the cabbage and soup in an even layer.
Save yourself some oven cleaning time and place the casserole dish on a baking sheet to catch any juices that might bubble up while this cooks.
Bake for 40-45 minutes or until the topping is a light golden brown and the cabbage filling is heated through and bubbly.
Allow casserole to rest for a few minutes before serving.