The definitions of tomato purée vary from country to world. In the USA, tomato purée is a processed food product, usually consisting of only tomatoes, but can also be found in seasoned form. It differs from tomato sauce or tomato paste in consistency and content; tomato puree generally lacks the additives common to a complete tomato sauce, and does not have the thickness of paste.
To prepare tomato purée, ripe tomatoes are washed and the leaves and stem are removed. Some processors remove the skin of the tomato as well. This is then mashed or mechanically chopped to the desired consistency.
Tomato purée can be used in soups, stews, sauces, or any other dish where the tomato flavor is desired, but not the texture. It is often deprecated by professional chefs, who find it to have an overly cooked flavor compared to other forms of canned tomatoes. This is sometimes a non-issue, as in long-cooked dishes, but in quick sauces such as a marinara sauce it is undesirable.
Tomato purée is sometimes referred to by its Italian name, passata di pomodoro, when it has been "passed" through a sieve to remove seeds and lumps. In this form, it is generally sold in bottles or aseptic packaging, and is most common in Europe.
In the United Kingdom, 'tomato purée' usually refers to what in America is known as concentrated tomato paste. In the UK, passata refers to sieved uncooked tomatoes.