A kilo of ripe tomatoes cooked down with onion, garlic and a pinch of sugar for half an hour, then blended. No tin, no herbs, and the sugar is there to correct the acidity rather than to sweeten it.
A kilo of tomatoes cooks down to roughly half a litre of sauce, which keeps about five days in the fridge and freezes well in portions. The sugar is not there to sweeten: a quarter teaspoon against a kilo of tomato is undetectable as sweetness and does its work on the acidity, which is why tinned sauces almost all contain some. If your tomatoes are very ripe you may not need it at all, so taste before adding. Blending with the skins in gives a thicker, more rustic sauce; straining gives a smoother one and loses a little volume.