Puree tomatoes in a blender, food processor or using an immersion blender and reserve.
If you want to remove the seeds, strain it through a large holed strainer.
Preheat a large saucepan over medium heat. Add olive oil and onions and saute onions about 5 minutes,
Add garlic and continue cooking several minutes more, avoiding browning the garlic.
Season lightly with salt and pepper. Add reserved tomato puree and oregano and cook over low
to medium heat for 20 minutes,stirring occasionally, until cooked to the desired consistency.
Add basil and blend. Serve immediately with your favorite spaghetti or pasta.