Add the beans, 2 tablespoons reserved bean liquid, tahini, lemon juice, garlic, oregano, salt, and pepper to the bowl of a food processor.
Process until completely smooth, scraping down the sides of the bowl as necessary. Taste and adjust the seasonings, as needed.
Enjoy immediately or transfer the dip to a covered container and refrigerate until ready to serve.
Before serving, give the dip a stir and sprinkle with a little sumac, if desired. Serve with assorted vegetables, crackers, and/or bread.
Notes
Be sure to reserve two tablespoons of the liquid from the can of beans before draining them. It's not necessary to rinse them.Leftover dip will last covered and refrigerated for 3-4 days or frozen for up to 3 months.