In a skillet over medium heat, add the 2 teaspoons of olive oil. Once hot, add the finely chopped onion and sauté until translucent and fragrant, about 3-4 minutes.
Add the 2 pounds of lean ground beef to the skillet, breaking it apart with a spatula. Cook until browned and fully cooked through, about 6-8 minutes. Drain any excess fat.
Stir in the garlic powder, onion powder, salt, black pepper, ketchup, and yellow mustard. Mix until everything is evenly coated and heated through. Remove the skillet from the heat.
Lay out four tortillas on a clean surface. Divide the beef mixture evenly among them, then sprinkle about 1 cup of shredded cheddar cheese over each. Top with the remaining tortillas.
Spray the skillet with cooking spray and heat over medium heat. Carefully place one quesadilla in the skillet and cook for 3-4 minutes, or until the bottom is golden brown. Flip and cook for an additional 3-4 minutes on the other side until crispy and the cheese is melted.
Remove the quesadilla from the skillet and let it cool for a minute. Use a sharp knife or pizza cutter to slice into wedges. Serve with optional toppings like diced tomatoes, sliced pickles, and shredded lettuce.
