01 - Heat olive oil in a skillet over medium heat. Add the chopped onion and sauté for 2 minutes until softened. Add the minced garlic and cook for 30 seconds until fragrant.
02 - Add ground beef to the skillet. Cook, breaking up the meat with a spoon, until browned throughout, about 5 minutes.
03 - Stir in tomato paste, honey or maple syrup, soy sauce, chili powder, cumin, salt, and pepper. Cook for 2-3 minutes until well combined and slightly thickened. Remove from heat and set aside.
04 - Lay out the flour tortillas flat. On one half of each tortilla, sprinkle a layer of shredded cheese. Spoon the beef filling over the cheese, then top with diced red bell pepper, diced green apple, and cilantro if using. Sprinkle additional cheese over the filling and fold the tortilla into a half-moon shape.
05 - Wipe out the skillet and return to medium heat. Melt butter or drizzle vegetable oil. Cook quesadillas one or two at a time, pressing down gently with a spatula. Flip once and cook until both sides are golden brown and crisp and the cheese is fully melted, about 2-3 minutes per side.
06 - Transfer cooked quesadillas to a cutting board and let rest for 1 minute. Slice into wedges and serve hot.