Heat olive oil in large skillet. Add the onion and sauté over medium heat for 6-8 minutes, until softened.
Add garlic in the skillet and continue to sauté for an extra 1-2 minutes.
Add the tomatoes, oregano, basil, and pepper. Bring sauce to a simmer over medium-high heat. Then lower the heat to keep sauce at a low simmer for 25 minutes. Stir occasionally.
Use an immersion blender to blend the ingredients until smooth. Can be blended in a regular blender in batches as well.
Add salt to taste. Serve warm. (This sauce keeps for up to 4 days in the refrigerator and up to 6 months in the freezer.)