Place all the ingredients into a blender or food processor. You can chop the onions into quarters and half the chillies and garlic beforehand for it to blend easily.
Blitz until you have reached your desired thickness.I used my Ninja blender and blitzed the ingredients for 12 seconds.
Optional: If you would like to thicken the sauce slightly. Heat a pan over a medium heat and add the sauce to it, leave to simmer for 5 to 10 minutes or until thickened, stirring occasionally.
