Preheat broiler. Brush the melted butter onto the corn. Broil 6 inches from the broiler for 10 minutes. Turn the corn over; broil 10 minutes longer. After cooling the corn, cut the kernels from the cob and set aside.
Heat the canola oil in a large heavy saucepan. Sear the pork cubes on all sides, stirring constantly for 10 minutes. Add the water, roasted corn, kidney beans, salt, and pepper. Bring to a boil, reduce heat to low, and simmer for 45 minutes longer.