01 - Heat olive oil in a skillet over medium heat. Add the onions and sauté for 2 minutes until softened. Add garlic and cook for another 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 to 3 minutes until well combined and slightly thickened. Remove from heat.
04 - Wipe out the skillet and place it back on medium heat.
05 - Lay out the tortillas flat. On one half of each tortilla, sprinkle a layer of shredded cheese, spoon on the beef mixture, then top with diced bell pepper, apple pieces, and cilantro if using. Sprinkle more cheese over the filling and fold the tortilla over to create a half-moon shape.
06 - Melt butter or drizzle oil in the skillet. Cook quesadillas one or two at a time, pressing down gently and flipping once, until both sides are golden and crisp and the cheese is melted, about 2 to 3 minutes per side.
07 - Transfer to a cutting board, let cool for 1 minute, then slice into wedges. Serve hot.