• Step 1: Preheat your oven to 375°F (190°C). In a large skillet, cook the ground beef over medium-high heat until browned and crumbled, about 5-7 minutes. Drain any excess fat.
• Step 2: Add the diced onion and minced garlic to the skillet, and sauté until the onion is translucent, about 3-4 minutes.
• Step 3: Stir in the black beans, pinto beans, diced tomatoes, and taco seasoning. Simmer the mixture for 5-7 minutes, allowing the flavors to meld.
• Step 4: In a separate bowl, prepare the cornbread batter according to the package instructions, using the milk and egg.
• Step 5: Spread the ground beef and bean mixture into a 9×13-inch baking dish. Carefully pour the cornbread batter over the top, and use a spatula to gently spread it into an even layer.
• Step 6: Sprinkle the shredded cheddar cheese over the top of the cornbread.
• Step 7: Bake the casserole for 25-30 minutes, or until the cornbread is golden brown and a toothpick inserted into the center comes out clean.
• Step 8: Let the casserole cool for 5-10 minutes before serving.