Baked sterlet in a royal way

I love the movie "Ivan Vasilyevich changes his profession." If I hear the expression "feast of the mountain" somewhere, I immediately remember both overseas caviar and red caviar. And the invariable attribute of the royal table is a baked sterlet in a royal way. A beautiful wonderful dish. It is not a shame to serve it both at the royal feast and at the wedding. That's just how to cook such a meal, making a discount on modernity? There will definitely be some friend who will provide the necessary recipe. Less than two days after my thoughts, a piece of paper with the necessary information appeared on my desk. Let's try to cook.
Defrost the sterlet and clean it of mucus, fish giblets, remove the gills.
Put the fish in boiling water for 3 minutes. After that, we will get rid of the fins on the belly and wash them. We do not touch the fins visible when feeding: on the ridge, on the tail and on the sternum.
In a deep bowl we prepare sauce for fish. Mix granulated sugar, soy sauce wine, pour lemon juice, pour spices and add onion rings.
Grease a baking sheet or a special form with fat, lay out the sterlet and pour the sauce well. In the oven, set the temperature to 180 degrees and bake for 20 minutes.
We spread it on a dish, use boiled potatoes for garnish, lemon slices for decoration, pour sauce for fish.