My own creation born out of desperation when I discovered vinegar was causing me to get Migraine headaches. Your Sumac has opened up a lot of doors, recipe-wise for me. I'm hoping by submitting this one I will be able to do the same for someone else. Sumac is not a well known herb [spice?]. Maybe we can change that a little.
I powder the shallots using a mortar & pestle, then mix the dry ingredients plus the sumac with the water and mix or shake well. Add the oil and mix or shake well again. Best after flavors are allowed to blend for several hours. I do not refrigerate.