Roughly dice the onions and finely dice the garlic and fry in the hot oil. Sweat the flour in it. Stir in the tomatoes with their juice, chop the tomatoes a little. Add the cream, ketchup, stock and oregano. Bring to the boil and simmer for approx. 10 minutes, season with salt, sugar and cayenne pepper.
Place the schnitzel in a greased baking dish. Pour the tomato cream over them. Let simmer in a preheated oven (175-200 ° C, fan oven 150-175 ° C) for 2 to 2 1/2 hours. Cover after 1 to 1 1/2 hours.
The schnitzel has to stew in the oven for a long time so that they become crispy. If the cooking time is too short, they will be tough. Don`t be stingy with the sauce, as a lot evaporates during cooking.