01 - Heat olive oil in a large skillet over medium heat. Add onion and cook until softened, about 3 minutes. Stir in garlic and cook for 30 seconds.
02 - Add ground beef to the skillet. Break it apart with a spatula and cook until browned and fully cooked, about 5 to 6 minutes. Drain excess fat if necessary.
03 - Mix in ground cumin, chili powder, smoked paprika, salt, and black pepper. Cook for 1 to 2 minutes until spices release their aroma. Remove from heat.
04 - Combine refried beans with lime juice and chopped cilantro in a small bowl, stirring until evenly blended.
05 - Lay tortillas flat on a work surface. Spread 2 tablespoons of bean mixture over half of each tortilla. Evenly distribute beef mixture on top, then sprinkle cheddar and Monterey Jack cheeses over the fillings.
06 - Fold each tortilla in half to enclose the fillings securely.
07 - Heat a large nonstick skillet or griddle over medium heat. Lightly brush the outside of each quesadilla with softened butter.
08 - Place quesadillas on the skillet and cook 2 to 3 minutes per side until golden brown and cheese is melted. Remove and let rest for 1 minute before slicing.
09 - Serve warm with salsa, sour cream, jalapeños, and fresh cilantro as desired.