You can buy ready prepared Harissa but it is no comparison to the flavour of homemade - see how easy it is to prepare
An hour or two ahead if possible place the chicken breasts in a shallow dish. Pour over the lemon juice, olive oil and seasoning.
Grill or barbecue until fully cooked.
To make the dressing: Put all the ingredients in a food processor. Process to form a thick sauce. Any leftovers will keep in the fridge for at least a week.
Serve with the chicken, some steamed new potatoes and vegetables or salad.