In a large skillet over medium heat, cook the ground beef until browned, breaking it apart with a spoon as it cooks. Drain any excess fat.
Stir in the taco seasoning mix and follow the package instructions, usually adding about 2/3 cup of water. Simmer for 5-10 minutes until the mixture thickens.
While the beef is cooking, prepare the rice according to package instructions if not already cooked.
In a large bowl or individual serving bowls, layer the cooked rice as the base.
Top the rice with the seasoned beef, black beans, corn, diced tomatoes, shredded lettuce, and shredded cheddar cheese.
Add a dollop of sour cream on top and garnish with jalapeños, diced avocado, and fresh cilantro if desired.
Serve immediately and enjoy!