01 - Rinse the brown rice under cold water. In a saucepan, combine rice, 2½ cups water, and ½ tsp salt. Bring to a boil. Reduce to low, cover, and simmer for 25 minutes until tender and water is absorbed. Fluff with a fork and set aside.
02 - While rice cooks, heat olive oil in a large skillet over medium heat. Add finely chopped onion and cook for 2 to 3 minutes until softened. Stir in minced garlic and cook for an additional 30 seconds.
03 - Add ground beef to the skillet, breaking it up with a spoon. Cook for 5 to 7 minutes until browned. Drain excess fat if necessary.
04 - Mix in chili powder, ground cumin, smoked paprika, dried oregano, salt, and black pepper. Stir in tomato paste and ⅓ cup plus 1 tbsp of water. Simmer for 4 to 5 minutes until the mixture thickens. Adjust seasoning to taste.
05 - Dice the avocado, halve the cherry tomatoes, drain the sweetcorn and black beans, and shred the lettuce and cheddar cheese.
06 - Divide the cooked brown rice evenly among four bowls. Top each with the seasoned beef mixture. Arrange avocado, cherry tomatoes, sweetcorn, black beans, shredded lettuce, and cheddar cheese on top. Add a dollop of sour cream, a lime wedge, and garnish with fresh cilantro leaves.
07 - Serve immediately, allowing each diner to mix their bowl as desired.