Cut your tomatoes in half and put them all in a saucepan.

Sprinkle with a pinch of salt, cover the saucepan and let the tomatoes simmer over moderate heat, stirring from time to time. After about 5-10 minutes, they should have softened and just begun to melt.

Pour the tomatoes into a food mill positioned over a large mixing bowl. Let the tomatoes cool off for a couple of minutes. By this time, depending on your tomatoes, there will be either a little or quite a bit of liquid that will have drained into the bowl. Discard it before proceeding.

Re-position the food mill on top of the bowl and rotate the handle until all you have left in the food mill are skins and seeds. You'll want to throw this stuff away, of course. What you'll have in the mixing bowl is your passata.

Transfer the purée into a mason jar or any other container you want. If you like, nestle a basil leaf or two in the passata. Let it cool off completely before closing the container.