In a medium pot over medium heat add in the olive oil.
When the oil starts to shimmer, add in the onions.
After 1 minute, add in the salt and stir to combine.
Continue cooking the onions for 5-9 minutes or until translucent.
Add in the garlic, stir and cook for 1 minute.
Add in the rest of the ingredients and stir.
Reduce the heat and cook on low for 25 minutes stirring occasionally.
Remove the pan from the heat and using an immersion blender, blend the ingredients until smooth and thick. If you do not have an immersion blender, pour the hot ingredients in a blender, cover but vent to allow the steam escape. You can cover the open lid with a kitchen towel as you start to blend on low to help avoid splattering.
Taste for seasoning and store in a glass jar in the fridge.