bring a large pot of water to a rolling boil. get another large bowl and fill with ice and water. when the pot's boiling, put tomatoes in and watch - you'll notice after about 1-5 min the skin breaking. immediately remove with a slotted spoon and submerge in the ice water. repeat until all the tomatoes have been boiled and chilled.
dump out the water, put the pot back on the stove and turn to medium low heat. add enough olive oil to the bottom to cover it in a thin film. add garlic and onion, salt, pepper, and oregano to taste after about 4 min - cook until soft, try not to brown the onion and garlic.
pull the skins off the tomatoes and toss. put the skinless tomatoes into a blender or food processor until liquefied.
add to the oil and reduce heat to low, cover. stir occasionally and simmer for 3 hours, take off the lid and let simmer uncovered for 1 hours wash basil, rip it up and mix in just before serving.