In a large skillet over medium heat, add the olive oil. Once hot, add the diced onion and bell pepper. Sauté for about 3-4 minutes until softened.

Add the minced garlic and cook for an additional minute.

Add the ground beef to the skillet, breaking it apart with a spatula. Cook until browned and no longer pink, about 5-7 minutes. Drain any excess fat.

Stir in the chili powder, cumin, salt, and pepper. Mix well and cook for another 2 minutes to combine the flavors. Remove from heat and let cool slightly.

Lay out four tortillas on a clean surface. Evenly distribute the beef mixture over each tortilla, then sprinkle with shredded cheddar cheese. Top with the remaining tortillas.

Wipe the skillet clean and return it to medium heat. Carefully place one quesadilla in the skillet. Cook for 3-4 minutes on each side until golden brown and the cheese is melted. Repeat with the remaining quesadillas.

Cut each quesadilla into wedges and serve with sour cream and salsa on the side.