In a skillet over medium heat, brown the ground beef until fully cooked. Drain excess fat and transfer the beef to the slow cooker.
Add the diced onion, bell pepper, and minced garlic to the slow cooker with the beef. Stir to combine.
Add the black beans, corn, diced tomatoes (with juices), and taco seasoning to the slow cooker. Mix well and season with salt and pepper to taste.
Cook on low for 6-8 hours or on high for 3-4 hours, stirring occasionally.
About 30 minutes before serving, sprinkle the shredded cheddar cheese over the top and arrange the frozen tater tots in a single layer on top of the cheese. Cover and continue cooking until the tater tots are golden and crispy.
Once done, garnish with fresh cilantro if desired, and serve hot.