Substituting tomato paste for tomatoes won't give you exactly the same texture or taste as when using tomatoes, but it comes close. Using tomato paste gives recipes a thicker puréed consistency than when using just tomatoes. Recipes using tomato paste won't have a fresh-tomato taste, but as tomato paste is still a tomato-based product, the taste will be similar.
Measure 2 tbsp tomato paste into a 1 cup measuring cup.
Pour enough water or tomato juice into the measuring cup to fill the cup.
Empty the tomato paste and water into a bowl. Whisk well to thoroughly combine.
Use in place of tomatoes in your cooked recipes.
This recipe is equal to 1 cup of tomato purée; make additional purée if your recipe calls for more tomatoes. Since tomato purée is less watery than cooked tomatoes, add extra water if your recipe needs it.