In a medium saucepan over medium, heat oil. Cook onion and garlic until soft and translucent, 10-12 minutes. Add all remaining ingredients except lemon juice. Reduce heat to low and simmer, uncovered, for 45 minutes. Allow to cool for 10 minutes.
Add sauce to blender jar. Blend on LO, gradually increasing to Speed 8 until smooth, about 45 seconds. Add lemon juice and pulse several times to combine. Serve immediately or store, covered, in refrigerator up to 1 month.