In a large skillet, heat 2 teaspoons of olive oil over medium heat. Add the finely chopped onion and sauté for about 3-4 minutes until softened.
Add the lean ground beef to the skillet with the onions. Use a spatula to break the beef apart as it cooks. Stir in 1 teaspoon of garlic powder, 3/4 teaspoon of onion powder, 1/2 teaspoon of salt, and 1/4 teaspoon of black pepper while the beef is browning. Cook until the beef is no longer pink, approximately 6-8 minutes.
Once the beef is cooked through, stir in 3 tablespoons of ketchup and 1 tablespoon of yellow mustard. Mix well and remove from heat.
Spray your skillet with cooking spray and place one tortilla in the skillet. Sprinkle about 1/2 cup of shredded cheddar cheese over half of the tortilla, then add a generous amount of the beef mixture on top of the cheese. Finally, sprinkle another 1/2 cup of cheese over the beef and fold the tortilla in half.
Cook for about 3-4 minutes on one side until golden brown and crispy. Carefully flip the quesadilla using the spatula, and cook for another 3-4 minutes on the other side. Repeat with remaining tortillas and filling.
Slice the quesadillas into wedges and serve hot with optional toppings like diced tomatoes, sliced pickles, or shredded lettuce for added freshness and crunch.
