Combine beans, corn, egg whites, cumin, chili powder, salt, 2 tablespoons of cornmeal, and 2 tablespoons of cilantro in a medium bowl and mix well. Divide the mixture into 8 balls. Place the remaining 4 tablespoons cornmeal on a plate. Roll the bean balls in the cornmeal to coat. Press each ball into a 1/2 inch thick patty.

Heat the oil in a large nonstick skillet to over medium heat. Add 4 of the cakes it the skillet and cool until crisp and golden on tho issued and heated through in the center, about 4 mins on each side. Transfer to a plate and cover with foil to keep warm; repeat w/ remaining patties. Meanwhile, combine the sour cream: lime zest, lime juice, and the reminding 2 tablespoons cilantro in a small bowl. Serve the bean cakes with the cilantro cream.