In order to make tomato purée from scratch, tomatoes are boiled and then ground in a grinder to make a paste.
As mentioned here, usually as I have been taught, one must always reduce the tomato paste till it is brick red in colour. No spices or flavours added yet. It is only tomato.
Example: For making a watery gravy, the tomato is reduced to brick red and then a great deal of water is added to make it almost as thin as water.
However I have a doubt whether it is always necessary to do so.
Question The question is, when should one reduce it to brick red and when should one stop midway? (To obtain what results one should reduce to brick red and to obtain what results must one stop midway)
(Please give one or two examples - For example, while making Spaghetti Arabiatta, should the tomato paste be reduced to brick red and add a little water later on OR should one stop mid way when the desired consistency is obtained? What will happen in either case? What is the logic to do either?