Preheat oven to 350°F.
Cook bacon in a skillet, drain, chop and set aside.
In the same skillet, saute the beef with the onion until brown. Remove and set aside.
Place the cabbage in a large microwavable casserole dish with cover, sprinkle in salt, tossing as needed.
Top cabbage with the thin butter slices, cover and microwave on high for 10 minutes.
Transfer half the cabbage to a 9x13 baking dish.
Top with the beef mix, then the bacon.
Place remaining cabbage on top.
Prepare the sauce by melting the 1/4 cup of butter in the skillet.
Add the heavy cream and water, sprinkle and whisk in the xanthan gum.
Cook on medium high heat until sauce is thickened. Remove from heat.
Whisk in the Cajun seasoning, salt and pepper; taste and adjust seasonings as needed.
Pour the white sauce over the top of the cabbage, beef, and bacon.
Cover with foil and bake at 350°F for about 30 minutes or until casserole is hot and bubbly and cabbage is cooked through.