Sauté the Aromatics: Heat olive oil in a frying pan over medium-high heat. Add chopped onion and sauté for 3-4 minutes until soft. Add minced garlic and cook for another minute.

Brown the Ground Beef: Add lean ground beef, breaking it apart with a spatula. Cook for 5-7 minutes, stirring frequently, until fully browned. Drain excess fat.

Create the Filling: Stir in taco seasoning, salt, and pepper. Add tomato purée and water or beef broth and simmer for 3-5 minutes until the sauce thickens.

Assemble the Quesadillas: Lay a tortilla on a surface, sprinkle cheddar cheese on half, add beef mixture, and more cheese before folding.

Cook the Quesadillas: Heat a pan over medium heat, place the quesadilla in it, cook for 2-3 minutes until golden. Flip using a spatula and cook for another 2-3 minutes.

Rest and Slice: Remove quesadilla to a cutting board, let it rest for a minute before slicing into wedges.