Heat a bit of olive oil in a pan...add one onion-finely chopped,and 2 cloves of garlic-crushed and finely minced. Cook over a medium heat til softened with no colour. Add 2 tins chopped tomatoes,1/2 to 1 tsp each Basil and Oregano, and a pinch of chilli flakes if wanted.Add a bit of salt to taste or 1/2 a veggie stock cube. Bring JUST to the boil,then simmer on a very low heat for 30-45 minutes. ...no less-otherwise the herbs will not have released their flavour,and the sauce will taste raw. Make sure the sauce does not dry out-add a bit of water.
You can do the same with finely chopped fresh tomatoes,adding some tomato puree to give the sauce more body. If using fresh-add a pinch of sugar-this takes away the acidity of the tomatoes.