Preheat your oven to 400°F and lightly grease a 9x13 inch baking dish. While the oven heats, dice the small onion into small pieces, mince the 2 garlic cloves, and dice the red bell pepper. Measure out the taco seasoning, cumin, cilantro, and have the diced tomatoes, tomato paste, and black beans ready nearby. This prep work ensures everything moves smoothly once you start cooking.

Heat 3 tablespoons of olive oil in a large skillet over medium-high heat. Add the ground beef and cook for 2-3 minutes, breaking it up with a spoon as it cooks. Once the beef is mostly browned, add the diced onion, minced garlic, and diced bell pepper. Continue cooking for another 2 minutes, stirring occasionally, until the vegetables are slightly softened and the garlic becomes fragrant. This builds a flavorful foundation for your casserole.

Add the 2 cups of cauliflower rice to the skillet and stir well to combine with the beef mixture. Cook for 1 minute to slightly soften the rice. Pour in the diced tomatoes and tomato paste, then add the taco seasoning, ground cumin, and black beans. Stir everything together until well combined and the tomato paste is fully incorporated. I like to taste the mixture at this point and adjust the salt and pepper to your preference—sometimes the taco seasoning varies in saltiness between brands, so it's better to check before baking.

Transfer the entire beef and vegetable mixture from the skillet into your prepared baking dish, spreading it evenly. Sprinkle the 2.5 cups of shredded cheddar cheese evenly over the top, making sure to cover most of the surface—this helps it melt uniformly and creates a golden, bubbly top.

Place the baking dish in the preheated 400°F oven and bake for 20-25 minutes, until the cheese is fully melted and the edges of the casserole are bubbling. The cooking time may vary slightly depending on your oven, so start checking around the 20-minute mark. I prefer to pull it out when the cheese has just turned golden at the edges—it gives the casserole better texture than pulling it out earlier.

Remove the casserole from the oven and let it rest for 2-3 minutes before serving. Garnish with the fresh cilantro right before serving for a bright pop of color and flavor that cuts through the richness of the cheese.