4 small corn tortillas or 2 whole wheat tortillas
Place tortillas in an oven-proof dish or baking tray. Mix corn, beans and rice together then spread to cover the tortillas and sprinkle with the cheese.
Put tostada into the oven until the cheese melts and the beans bubble around the edges, about 7 minutes.
Take the dish out of the oven and top each 'tostada' with chopped lettuce, tomato salsa, chopped scallions and chopped cilantro. Cut into 4 portions and serve immediately.