In a large skillet over medium heat, add olive oil and sauté the chopped onions until translucent, about 2 minutes.
Add the minced garlic and diced chicken to the skillet. Cook until the chicken is browned and cooked through, stirring occasionally.
Sprinkle ground cumin, chili powder, paprika, cayenne pepper, salt, and pepper over the chicken. Stir well to coat the chicken evenly with the spices. Cook for another 2-3 minutes to allow the flavors to meld together.
Add the drained black beans to the skillet and stir until they are heated through.
Warm the flour tortillas in a separate pan or microwave.
To assemble the burritos, lay out each tortilla and spoon the chicken and bean mixture down the center.
Top with cooked rice, shredded cheddar cheese, diced tomatoes, shredded lettuce, diced avocado, and chopped cilantro.
Fold the sides of the tortilla inward, then roll it up tightly from the bottom to create a burrito.
Wrap each burrito in aluminum foil to keep them warm and to help hold their shape.
Serve immediately, or you can place the wrapped burritos in a preheated oven at 350°F (175°C) for 5-7 minutes to melt the cheese further.