To prepare the tomato puree, remove the stalks and wash the tomatoes very well, then put them to drain. Cut each tomato in half and remove the seeds.

Place them in a large pot and let them dry over low heat by covering them with a lid, stirring occasionally, until they are limp and pulped. At this point, pass them with a vegetable mill, making the sauce converge in a smaller steel pot. If the tomato puree seems to have the right density, bottle it. Otherwise, filter it with a fine mesh strainer to remove excess water or let it thicken on the stove until it reaches the desired consistency.

Meanwhile, sanitize the jars by boiling them in a pot plenty of water.

Put some basil leaves inside each sanitized jar. Pour the tomato puree into the sanitized jars with the help of a funnel and taking care to leave 2-3 cm of space from the edge of the jar. Finish with a few more basil leaves and close the jars well. At this point, proceed with boiling.

Once the jars are cold, check that the vacuum has been done correctly: if, by pressing the cap, you DO NOT hear the "click clak", the vacuum will have formed correctly. Store the tomato puree in a cool place away from light.

The tomato puree can be kept for about 1 year, as long as the jars have been properly vacuum-sealed.