Preheat oven to 425°F.
Get out two 18×13-inch sheet pans and very lightly spray just one of them with nonstick cooking spray.
In a large skillet, over medium heat, add olive oil, bell peppers, and yellow onion. Cook for 5 minutes, stirring often to ensure evenly cooked vegetables.
Add ground beef and minced garlic to the bell peppers and onions. Cook until completely browned.
Remove from the heat and drain the excess fat.
Return the meat mixture to the skillet. Add chili powder, cumin, paprika, kosher salt, black pepper, black beans, black olives, and salsa. Stir well after adding each ingredient.
Place 6 of the flour tortillas around the edges of the lightly sprayed sheet pan. Make sure the tortillas overlap and are hanging halfway over the edge of the pan, leaving a gap in the center.
Place 1 tortilla over the bottom center gap of the sheet pan.
Evenly spread the meat mixture over the tortillas.
Sprinkle cheese on top of meat, then top with sliced green onions.
Place the final tortilla over the top center of the mixture.
Starting at either side of the sheet pan, carefully but tightly begin folding the tortillas towards the middle.
When all sides are folded, place the second sheet pan on top of the folded tortillas. This is to ensure edges do not come apart during baking.
Bake for 20 minutes.
Remove pans from the oven. Remove the top sheet pan and cook for an additional 5 minutes.
Remove from the oven and allow the quesadilla to slightly cool before cutting into servings.
Serve with sour cream, if desired.