Heat the olive oil in a large skillet over medium heat.
Add the chopped onion and bell pepper to the skillet and sauté for about 5 minutes, until softened.
Add the ground beef to the skillet. Cook until browned, breaking it apart with a spatula, about 5-7 minutes.
Stir in the taco seasoning, cooked rice, black beans, garlic powder, salt, and pepper. Cook for an additional 3-4 minutes, mixing well until heated through.
Remove the skillet from heat and stir in ½ cup of shredded cheddar cheese until melted and well combined.
Lay a flour tortilla on a flat surface. Spoon a generous amount of the beef and cheese mixture onto the center of the tortilla.
Fold the sides of the tortilla over the filling, then roll from the bottom up to create a tight burrito. Repeat with remaining tortillas.
In the same skillet, place the burritos seam side down and cook for 2-3 minutes on each side until they are crispy and golden brown.
Serve the burritos warm topped with remaining cheddar cheese, salsa, sour cream, and garnish with fresh cilantro if desired.