Heat the olive oil in a large pan.  Add the onions and cook over medium low heat for 6-8 minutes till softened.  Add the garlic, stir well and cook for 2 minutes or so.  Add the tomatoes, tomato paste and all the herbs and seasonings.  Mix well and simmer over medium low(with a spatter guard over the pan) for about 1 - 1 1/2 hours stirring occasionally till the right consistency is reached.  We usually like the sauce really thick but it's up to you how long you want to cook it.

You can also increase the heat and stir it more frequently to have it done faster, but I like to just leave it on the stove and forget about it over low heat for most of an afternoon usually.  The great thing is, if it's too thick you can always add a little water.  Also you can take an immersion blender to it, or throw it all in a blender and blend it till smooth if that's what you like.  Plus, it makes awesome leftovers, so if don't have time on weeknights, you can make some(or even double it) and have leftovers all week.  Or you can use the sauce anywhere you would use bottled or canned pasta sauce.  And it's so easy to make :D