01 - Preheat the oven to 400°F for baking the assembled casserole.
02 - Heat olive oil in a large ovenproof skillet or Dutch oven over medium heat. Add diced onion and minced garlic; sauté for 3 minutes until softened and fragrant.
03 - Stir in diced red and green bell peppers; cook for 3 additional minutes until slightly softened.
04 - Add ground beef to the skillet. Cook, breaking up with a wooden spoon, until browned, approximately 6-8 minutes. Drain excess fat if desired.
05 - Stir in tomato paste until incorporated. Add diced tomatoes, kidney beans, black beans, chili powder, cumin, paprika, oregano, cayenne, salt, black pepper, and beef broth.
06 - Simmer uncovered for 15 minutes, stirring occasionally, until mixture thickens slightly.
07 - While chili simmers, whisk together cornmeal, flour, sugar, baking powder, and salt in a medium bowl.
08 - In a separate bowl, whisk milk, eggs, and melted butter until combined. Pour wet ingredients into dry mixture and stir until just combined, being careful not to overmix.
09 - Spread cornbread batter evenly over the hot chili mixture.
10 - Bake uncovered for 25-30 minutes until cornbread is golden brown and a toothpick inserted in the center comes out clean.
11 - Allow casserole to rest for 10 minutes before serving to set the cornbread topping.