01 - Heat olive oil in a large skillet over medium heat and sauté the chopped onion for 2 minutes until softened.
02 - Add minced garlic to the skillet and cook for 30 seconds until fragrant.
03 - Add ground beef and cook, breaking it up with a spoon, until browned, approximately 5 to 6 minutes.
04 - Stir in chili powder, ground cumin, smoked paprika, salt, and black pepper and cook for 1 minute to toast spices.
05 - Add tomato sauce, mix well, and simmer for 2 to 3 minutes until slightly thickened. Remove from heat.
06 - Wipe out skillet and return to medium heat.
07 - Place one tortilla on a plate, sprinkle with a blend of cheddar and Monterey Jack cheese, spoon about one quarter of the beef mixture over half the tortilla, top with more cheese, then fold tortilla in half.
08 - Melt some butter in the skillet, then cook the folded tortilla for 2 to 3 minutes per side until golden brown and cheese is melted.
09 - Repeat assembly and cooking with remaining tortillas and filling.
10 - Cut quesadillas into wedges and serve hot with optional sour cream, salsa, fresh cilantro, and lime wedges.