Slice the beef thinly.
Julienne the onion and bell pepper.
Season the beef with soy sauce, sugar, minced garlic, sesame oil, and pepper.
Stir-fry the beef and vegetables in a pan.
Place the stir-fried mixture and cheese on a tortilla.
Fold the tortilla in half and grill on both sides until golden brown.
Cut into bite-sized pieces.