Saute onion in olive oil until very soft (about 5 minutes). Add tomato paste, water, spices and orzo. Bring to boil and cook for 20 minutes stirring about every 5 minutes (do not cover). Stirring makes it kind of creamy.
This recipe was one that my Greek mother in law passed on to me. She made it for us often only she simmered roast in with it. I think the veggie version is just as good.