In the food processor blend the chick peas, tahini, garlic, lemon juice, olive oil, and cumin until smooth. Add enough water to slightly thin it out. Season with salt and pepper. Remove from the processor and place in a pretty dish. Heat 1/2 tablespoon of the remaining olive oil in a skillet large enough to fit the pita bread. Throw in the oregano springs, and top with the pita bread. Hold the pita bread down with one hand and with your other hand squeeze the juice from one half of the lemon around the rim of the pan so it goes down into the pan , under the pita. Hold the pita in place until you feel it begin to heat through. Flip it over and cook for 2 minutes longer. Repeat with the other pita. Cut the pita into 4 wedges. Smear on some hummus and top with tomatoes and cucumbers.