*It's best to use Cento tomato puree or Pomi strained tomatoes (links provided in the article above). Both are Italian brands. Cento is easier to find in regular supermarkets. They are sweeter and less acidic than American brands. If using an American brand such as Muir Glen Tomato Puree, you might need to add a small amount of a sweetener to balance out the acidity of the tomatoes.