Step 1: Brown the beef - Start by browning the ground beef in a skillet over medium heat. Break it up as it cooks and drain off any excess grease. This step adds flavor and keeps the casserole from becoming greasy.
Step 2: Add everything to the slow cooker - Add the cooked beef to your slow cooker along with the diced onion, taco seasoning, uncooked rice, beef broth, black beans, corn, salsa, and one cup of the shredded cheese. Stir everything together until well combined.
Step 3: Fold in the tortillas - Gently fold in the tortilla pieces, pressing them down slightly so they are mostly covered by the liquid. This helps them soften evenly as they cook.
Step 4: Slow cook - Cover and cook on low for four to five hours. If you can, give it a gentle stir about halfway through to prevent sticking around the edges.
Step 5: Add the cheese topping - Once the rice is tender, sprinkle the remaining shredded cheese evenly over the top. Cover again and cook for another twenty to thirty minutes until the cheese is fully melted.
Step 6: Let it rest - Turn off the slow cooker and let the casserole rest for about ten minutes. This helps everything set and makes it easier to scoop and serve.