Heat the 2 1/2 tablespoons of olive oil in a medium sized enamelled or stainless steel saucepan and cook the finely chopped onions in it over a moderate heat, stirring frequently, for 7 to 8 minutes.

When the onions are soft and transparent but not brown, add the finely chopped garlic and cook for another 1 to 2 minutes, stirring constantly.

Then stir in the coarsely chopped tomatoes and their liquid, the tomato purie, oregano, basil, bay leaf, sugar, salt and a few grindings of black pepper.

Bring the sauce to a boil, turn the heat very low and simmer uncovered, stirring occasionally, for about 1 hour.

When finished, the sauce should be thick and fairly rough in texture.

Remove the bay leaf.

Taste and season the sauce with salt and freshly ground black pepper.

If you want a smooth texture, purie the sauce through a food mill, or rub it through a sieve with the back of a large wooden spoon.