In a large skillet, heat the frying oil over medium heat. Add the ground beef and cook until browned, breaking it into small pieces with a spatula. Drain any excess fat.

Stir in the diced onion and bell pepper, cooking until the vegetables are tender. Add the taco seasoning, Worcestershire sauce, tomato paste, cumin, garlic powder, onion powder, cayenne pepper, paprika, and coriander. Mix well and cook for another 2-3 minutes until everything is combined and heated through.

If you're using black beans, add them to the skillet and stir until warmed. Remove the skillet from heat and drizzle with lemon juice, stirring to combine.

Place a tortilla on a clean surface and spread a portion of the beef mixture on one half. Sprinkle cheese generously over the filling. Fold the tortilla in half to cover the filling.

Heat a non-stick pan or griddle over medium heat. Carefully place the folded quesadilla in the skillet and cook for about 3-4 minutes until the bottom is golden brown and the cheese begins to melt. Flip the quesadilla and cook for an additional 2-3 minutes on the other side.

Once cooked, remove the quesadilla from the skillet and let it rest for a minute before cutting it into wedges. Serve with salsa, guacamole, and sour cream, if desired.