Scald the tomatoes in boiling water for 15 minutes and remove. Remove and discard the peels, and halve. Remove the stems, seeds and excess juice from the tomatoes, place them in a blender, and blend them to a smooth puree.
Sauté the onion in the hot olive oil until glassy. Add the minced garlic and stir frequently for another minute or so. Add the tomato puree, the herbs and the seasoning. Stir well and allow to gently simmer half covered for 45 minutes to an hour (remove lid after 20 minutes). This will depend on the ripeness and character of the tomato used. Stir occasionally.
The sauce should be nice and thick. Stir in a teaspoon more of olive oil (optional).