01 - Rinse brown rice under cold water. In a saucepan, combine rice, water, and salt. Bring to a boil, then reduce heat to low, cover, and simmer for 25 minutes until tender and water is absorbed. Fluff with a fork and set aside.
02 - While the rice cooks, heat olive oil in a large skillet over medium heat. Sauté the finely chopped onion for 2 to 3 minutes until softened. Add minced garlic and cook for 30 seconds until fragrant.
03 - Add ground beef to the skillet, breaking it apart with a spoon. Cook until evenly browned, approximately 5 to 7 minutes. Drain excess fat if necessary.
04 - Incorporate chili powder, cumin, smoked paprika, oregano, salt, and black pepper into the beef. Stir in tomato paste and water, mixing thoroughly. Simmer the mixture for 4 to 5 minutes until thickened. Adjust seasoning to taste.
05 - Dice avocado; halve cherry tomatoes; drain canned sweetcorn and black beans; shred lettuce and cheddar cheese.
06 - Divide cooked brown rice evenly into four bowls. Layer with the seasoned beef mixture, then top with avocado, tomatoes, corn, black beans, shredded lettuce, and cheddar cheese. Add a dollop of sour cream, a lime wedge, and fresh cilantro leaves to each serving.
07 - Serve immediately, allowing diners to mix ingredients as desired.