Heat a large pot over medium heat. Add the ground beef, diced onion, and minced garlic. Cook until the beef is browned and the onion softens, breaking up the meat as it cooks.

Stir in the kidney beans, diced tomatoes, chili powder, cumin, salt, and black pepper. Bring the mixture to a simmer, then reduce the 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, whisk together the cornmeal, flour, and baking powder.

In a separate bowl, whisk the milk, egg, and vegetable oil. Pour the wet ingredients into the dry ingredients and stir just until combined.

Pour the cornbread batter into a greased 8-inch square baking pan. Bake for 20 minutes, or until the top is golden and a toothpick inserted in the center comes out clean.

Let the cornbread cool for a few minutes, then cut into squares and serve alongside the chili.