Squeeze out and discard the juice and seeds from tomatoes, place the tomato pulp in a saucepan, and boil without water for 30 minutes, constantly stirring. Rub the pulp through a fine sieve, return to the saucepan, and boil until it thickens. Spread thinly with a knife on a baking sheet greased with olive oil. Set in the oven after baking bread or dry in the open air in the shade. Cut into pieces, wrap in paper, and store in a cold, dry place. Use in sauces and other dishes.