In a large skillet over medium heat, cook the ground beef until browned. Drain excess fat if necessary.
Stir in the chopped onion, garlic, and bell pepper. Cook until softened, about 5 minutes.
Add the diced tomato and optional potatoes to the skillet. Cook for an additional 5-7 minutes until the potatoes are tender.
Stir in the chopped olives, tomato paste, cumin, chili powder, salt, and pepper. Cook for another 2-3 minutes until everything is well combined.
Heat a separate skillet over medium heat. Add a small amount of oil to coat the bottom.
On one half of each tortilla, place a generous portion of the picadillo filling and top with shredded cheese. Fold the tortilla over to create a half-moon shape.
Place the folded quesadilla in the hot skillet and cook for 2-3 minutes on each side, or until golden brown and crispy. Repeat for remaining tortillas.
Once cooked, remove the quesadillas from the skillet and let them cool for a moment. Slice into wedges and prepare for serving.