Preheat oven to 375°F; grease a 9x13-inch dish and set aside.
Cook beef and onion in large skillet over medium-high about 8 minutes until beef is browned and onion tender; drain excess fat.
Stir in beans, corn, tomatoes with chilies, enchilada sauce, cumin, chili powder, and salt. Simmer 5 minutes; pour into dish and top with 2 cups cheese.
Whisk cornmeal, flour, and baking powder in large bowl; beat eggs, milk, and oil separately.
Stir wet into dry ingredients just until combined; pour evenly over meat and cheese.
Bake uncovered 35-40 minutes until topping is golden brown and set. Top with remaining 1 cup cheese; bake 5 minutes until melted. Stand 10 minutes before serving.