1. Heat butter in a skillet over medium heat. Add diced bell pepper and onion, cook until softened.
2. Pour beaten eggs into the skillet. Cook, stirring occasionally, until scrambled and fully cooked. Season with salt and pepper.
3. Lay out tortillas on a flat surface. Divide scrambled eggs evenly among the tortillas, placing them on one half of each tortilla.
4. Sprinkle shredded cheese over the eggs. Fold the tortillas in half to cover the filling.
5. Heat a clean skillet over medium heat. Cook each quesadilla for 2-3 minutes on each side, until the tortilla is golden brown and the cheese is melted.
6. Let the quesadillas cool slightly, then cut into wedges. Serve immediately or wrap in foil and refrigerate for up to 3 days.