In a large skillet over medium heat, cook the ground beef until browned, breaking it up into crumbles as it cooks (about 5-7 minutes). Drain excess fat if necessary.
Stir in the taco seasoning, salt, and pepper. Add the black beans and cooked white rice, mixing well. Cook for an additional 2-3 minutes.
Remove the skillet from heat and stir in the taco sauce and half of the shredded cheddar cheese until fully mixed.
Lay one tortilla flat and spoon a generous portion of the beef mixture onto the center. Top with a dollop of sour cream, diced tomatoes, and a sprinkle of the remaining cheddar cheese.
Fold the sides of the tortilla over the filling, then roll it from the bottom up to form a burrito. Repeat with the remaining tortillas and filling.
For a melty finish, place the burritos on a baking sheet and sprinkle with any leftover cheddar cheese. Bake in a preheated oven at 375°F (190°C) for about 10 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let cool slightly. Garnish with chopped cilantro before serving.