01 -
Finely chop the red onion, chop the cilantro and crush one clove of garlic and add to a small-medium size glass bowl.
02 -
Add the rest of the ingredients, the mayonnaise, one tablespoon of lemon juice, 3 tablespoons of harissa paste, tomato paste, cumin, and sugar. Whisk well with a fork or balloon whisk until all the ingredients are well-incorporated.
03 -
Taste, and adjust the seasoning. Add up to one tablespoon more lemon juice for tang, an extra crushed clove of garlic if you want it more garlicky, and up to three more tablespoons of harissa paste for a spicier sauce. Remember the sauce will get spicier and stronger as it sits.
04 -
Use straight away, or if you have time, preferably refrigerate the sauce for at least an hour to let the flavors develop more.