1. Heat the olive oil in a large skillet over medium-high heat. Add the diced onion and green bell pepper and cook for 3–4 minutes, until softened and fragrant. Stir in the minced garlic and cook for 30 seconds more.

2. Add the ground beef to the skillet, breaking it up with a spoon, and cook until browned and no longer pink. Drain off any excess grease if necessary.

3. Stir in the tomato paste, tomato sauce or mild salsa, chili powder, cumin, smoked paprika, dried oregano, salt, black pepper, and crushed red pepper flakes if using. Add the beef broth or water and simmer for 5–7 minutes, stirring occasionally, until the mixture thickens and is saucy but not runny. Remove from the heat and let cool for about 5 minutes.

4. Warm the flour tortillas in a dry skillet or microwave until soft and pliable. Lay one tortilla on a flat surface. Sprinkle some cheddar and Monterey Jack cheese down the center, then spoon a portion of the beef mixture over the cheese.

5. Fold the sides of the tortilla over the filling, then roll it up tightly from the bottom to form a chimichanga, placing it seam-side down. Repeat with the remaining tortillas, beef mixture, and cheese.

6. Brush each chimichanga lightly with melted butter or vegetable oil. To pan-fry, heat a thin layer of oil in a large skillet over medium heat and cook the chimichangas, starting seam-side down, turning every couple of minutes until all sides are golden and crispy.

7. Alternatively, to bake, place the brushed chimichangas on a parchment-lined baking sheet and bake at 400°F (200°C) for 15–20 minutes, turning once, until crisp and lightly browned.

8. Serve the chimichangas hot, topped with shredded lettuce, diced tomatoes, diced white onion, cilantro, sour cream, guacamole, salsa, and lime wedges for squeezing over the top.