Wash the tomatoes well, cut off the stems, peel and deseed them.
Quarter them
Place them in a food processor
And blend them.
Place them in a large pot,
Add plenty of salt and let the tomatoes boil for quite some time, until all the liquids are absorbed to a concentrate.
If you like you can add a sprig of basil to the tomatoes while they are boiling, it will give the sauce a nice flavor, ideal for pizzas and pasta.
When you have a concentrate of your liking, take the jars that you are going to use and as the sauce is piping hot, pour it in leaving a small space on top (be careful to not burn your hands). Pour a little oil on top and seal immediately with the lid.
Turn the jars upside down and set them aside until they cool thoroughly. They might allow some oil to seep through, so set them aside somewhere where this won't be a problem.
When they cool, set them straight and store in the cabinet until you need to use them. They are airtight now and they will keep for the whole of winter. When you open a jar then you have to store it in the fridge. It will keep there up to a month as long as when you use some, cover what remains with oil.
