Place a medium saucepan over medium heat and the olive oil. Once the oil is hot, add the chopped onion stirring often until soft and golden (about 5 min). Add minced garlic and stir 1 min, or until fragrant.
Stir in the crushed tomatoes, oregano, salt, and pepper. Bring to a light boil then reduce heat and simmer partially covered for about 15 minutes.
Add the fresh basil, then allow the sauce to cool and blend until smooth using an immersion or regular blender.