1. Heat a large skillet over medium heat and cook the chopped onion for 3 to 4 minutes until softened. Add the garlic and cook for 30 seconds.

2. Add the ground beef and cook until browned, breaking it up with a spoon as it cooks. Drain excess grease if needed.

3. Stir in the taco seasoning, tomato paste, water, salt, and black pepper. Cook for 2 to 3 minutes until the beef is well coated and slightly saucy.

4. In a bowl, combine the shredded cheddar and mozzarella cheese.

5. Lay the tortillas flat. Spoon the beef mixture onto one half of each tortilla, then top with the cheese mixture.

6. Fold each tortilla over to make a half-moon shape.

7. Lightly grease a skillet with butter or oil and cook the quesadillas over medium heat for 2 to 3 minutes per side until golden brown and crisp and the cheese is melted.

8. Transfer to a cutting board, let rest for 1 minute, then slice into wedges and serve warm.