01 - Heat olive oil in a large skillet over medium heat. Add chopped onions and cook until softened, about 2 minutes. Add minced garlic and sauté for 30 seconds until fragrant.
02 - Add ground beef to the skillet and cook, breaking it up with a spatula, until browned, about 5 minutes. Stir in taco seasoning, salt, pepper, tomato paste, and water. Simmer for 2–3 minutes until the mixture thickens. Remove from heat.
03 - Heat tortillas in a dry skillet or microwave until pliable and easy to fold.
04 - Lay each warm tortilla flat. In the center, layer one-fourth of the rice, beef mixture, black beans, diced tomato, salsa, sour cream, and an equal mix of both shredded cheeses. Sprinkle with cilantro if desired.
05 - Fold in both sides of the tortilla toward the center, then roll up tightly from the bottom to form secure burritos.
06 - Spread a thin layer of softened butter evenly over the exterior of each burrito for golden grilling.
07 - Heat a large skillet or griddle over medium heat. Place burritos seam-side down and grill for 2–3 minutes per side, pressing gently with a spatula, until the tortillas are golden brown and crispy with melted cheese inside.
08 - Slice each burrito in half diagonally and serve immediately while hot and crispy.