Preheat oven to 425°F. Lightly grease a 2-quart baking dish; set aside.
In a large skillet over medium-high heat, cook the ground beef and onion until the meat is no longer pink and the onions are translucent (about 7-10 minutes). Add the garlic and cook for 30 seconds longer. Drain off the fat.
Stir in the corn, tomato soup, water, chili powder and salt. Reduce heat to low and simmer for about 15 minutes. Transfer the beef mixture to the prepared baking dish.
In a medium bowl, stir together the cornbread mix, egg, and milk.
Spread the batter over the beef mixture.
Bake at 425°F for 18-20 minutes, or until golden brown and the topping is cooked through. Let stand for about 5-10 minutes before serving.
