Preheat oven to 300°F.
Pat the beans dry with a paper towel and place into a food processor. Add in the onion, garlic, parsley, flour, spices and seasonings, and process until fairly smooth and very thick – so you can form patties.
Preheat a large, nonstick skillet with the vegetable oil. Form 4 large patties and cook 3 minutes on each side.
While the patties are cooking, get the sauce started: Place the tahini paste in a medium-size mixing bowl and add the water, lemon juice and zest, salt and freshly ground black pepper. Set sauce aside for falafel burger assembly.
Cut of the edge of each pita to form big pockets then wrap them in foil and place in the preheated oven to warm, about 3 minutes.