Slice the onion into thin slices with either a sharp knife or you can also use a mandolin. Optional - allow the onions to soak in a bowl of water for 10 minutes for a lighter onion taste then drain.
Roughly chop up the parsley leaves.
Add the onion slices to a bowl with the sumac, lemon juice, olive oil, salt and chopped parsley. Stir well continuously to ensure all the onions are coated in the sumac and the dressing.
Allow it to marinate for 5 minutes for the flavors to develop and then serve up your delicious tangy Sumac Onions alongside a bbq, kebab or in a falafel wrap!
