This recipe I first found on Foodnetwork.com and misplaced it and today came across it in the The Province Newspaper. I love trying new recipes and this was a good recipe for lamb. Sumac is a reddish spice from Middle East that is slightly sour , lemony taste. Look for bags of it ( usually ground ) at Middle Eastern grocery stores and I have found in Real Canadian Superstore. If you can't find it substitute finely grated zest of one lemon.