Brown the ground beef in a large pot over medium heat. Break it up with a spoon until no pink remains.
Add the diced onion, garlic, and bell pepper to the pot. Cook for five minutes until the vegetables soften.
Stir in the diced tomatoes, kidney beans, chili powder, cumin, beef broth, salt, and black pepper. Bring the mixture to a simmer.
Lower the heat and let the chili cook uncovered for 25 minutes, stirring now and then.
While the chili simmers, heat the oven to 400 degrees. In a mixing bowl, whisk together the cornmeal, flour, baking powder, and sugar.
In a separate bowl, whisk the milk, egg, and melted butter. Pour the wet mixture into the dry ingredients and stir until just combined.
Pour the cornbread batter into a greased 8-inch baking dish. Bake for 20 minutes until the top is golden and a toothpick comes out clean.
Serve the chili in bowls with squares of warm cornbread on the side.