Add tomato puree, dry herbs and spices, cover with lid and cook for 15 minutes on low heat. Remove the lid. Continue cooking and stirring until most of the liquid is evaporated. Taste it. Balance the taste with sugar and salt. If tomatoes were not sour enough, you need to add vinegar. The flavor of this mixture is, ideally, very rich and complex. It has to reflect the balanced combination of sourness and sweetness, be sufficiently salty, and capture the earthiness of the root vegetables. It is very important to preserve the intensity of all four of these flavors so that they are still present after the mixture is diluted with the relatively large volume of liquid broth.