I don’t have any experience with Rumtopf - though it sounds wonderful.
Hopefully someone here will have some knowledge to share.

OVEN-BAKED SALMON / EASIEST SAUCE EVER / Makes 4-8 servings / Do not freeze
SAUCE Add 8 oz (tubful) of water to 8 oz tub cream cheese with chives and onions in microwaveable dish.
Micro til it just starts to bubble. Add a little pepper.
SERVE over baked salmon......add a shower of fresh chives.