Preheat oven to 375°F.
In a heavy skillet, sauté ground beef and yellow onions, until browned.
Add garlic, chili powder, cumin to the beef and onions, cook for one minute.
Stir in tomatoes and simmer for 10 minutes. Remove from heat and stir in black beans.
In a mixing bowl, combine cornmeal, flour, sugar, baking powder, and baking soda.
Whisk in milk, eggs, and butter to combine with the cornmeal mix.
Pour meat chili mixture in a prepared 9 x 13 deep baking dish. Top with cornbread batter.
Bake for 35 minutes.