In a large skillet or Dutch oven, heat olive oil over medium-high heat. Add ground beef, breaking it apart. Cook for 6-8 minutes until browned. Drain excess fat.

Reduce heat to medium and add chopped onion and bell pepper. Sauté for 5-7 minutes until softened. Stir in minced garlic for another minute.

Stir in chili powder, ground cumin, smoked paprika, and cayenne pepper. Cook for 1 minute to toast spices.

Pour in diced tomatoes and water or beef broth. Simmer, covered, for 10-15 minutes, seasoning with salt and pepper.

Lay a tortilla flat. Sprinkle ¼ cup each of Monterey Jack and cheddar cheese over half. Spoon ½ cup of beef filling over cheese, top with another ¼ cup of cheese, and fold.

Heat a skillet over medium heat and add butter or oil. Cook quesadillas for 3-4 minutes per side until golden brown. Repeat with remaining quesadillas.

Remove quesadillas, slice into wedges, and serve immediately with desired toppings.