Roughly dice the tomatoes with the skin on. Put in a large saucepan, add a little salt and bring to the boil. Then let the tomatoes simmer on a low flame for about 1 hour.
Then pass everything through a fine sieve. Season the collected liquid with salt and pepper to taste and bring to the boil again. Fill the boiling juice to the brim in previously rinsed glass bottles and screw them on immediately.
The juice will then easily keep for over a year. With about 20 tomatoes I get about 1.5 liters of juice. Ideal for tomatoes that are already too soft and that are then usually no longer eaten.