Place beans in a large bowl and mash until smooth. Add onion, parsley, salt, pepper, cumin, baking powder and flour. Stir until combined into a paste. Place bowl in refrigerator for 1 to 4 hours.
In a medium bowl, combine all sauce ingredients. (Can be made a day ahead and stored in airtight container.)
In a large bowl, add lettuce, onion, tomatoes, salt and olive oil. Toss to combine.
Using a 1/8 measuring cup, scoop out garbanzo bean mixture. Form into balls and place on a sheet tray. Fill a cast-iron skillet halfway with oil. When hot cook the falafel, turning until golden brown. Remove to a towel-lined plate.
To plate: Place salad on a plate. Top with falafel balls. Drizzle with yogurt sauce. Serve with pita wedges on the side.