Preheat the oven to approx. 190 - 200 ° C top / bottom heat.
Let the fish thaw a little and season with salt and pepper.
Finely dice onion and garlic and fry in olive oil in a pan. Add the vegetables, season with salt, pepper and the herbs and fry everything a little more. Then deglaze with vegetable stock. Add the tomato paste, stir in and cook everything with the lid on for 5 minutes. Then stir in Cremefine and bring to the boil. Possibly season again.
Put everything in a baking dish, put the fish on top. Spread the sour cream on the fish and put everything in the oven. Bake for 25-30 minutes.