Heat a large pot over medium heat and add the ground beef. Cook until browned, breaking it up with a spoon, then drain excess fat.

Add the diced onion and minced garlic to the pot. Stir and cook for 3 minutes until the onion softens.

Stir in the chili powder, cumin, salt, and black pepper. Cook for 1 minute to toast the spices.

Add the drained kidney beans and diced tomatoes with their liquid. Bring to a simmer, then reduce heat to low and cook uncovered for 20 minutes, stirring occasionally.

While the chili simmers, preheat the oven to 400°F. In a mixing bowl, combine 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.

Let the cornbread cool for 5 minutes, then cut into squares and serve with the chili.