Preheat oven to 425 degrees.
In a large skillet, brown ground beef, onion, and green bell pepper until beef is no longer pink (about 8 minutes). Drain, then add in beans, taco seasoning, and salsa. Let simmer for about 5 minutes to let the flavors meld together.
Lightly spray a cookie sheet with non-stick cooking spray. Place 6 tortillas around the edges of the pan so that half of each tortilla hangs off the pan and the edges are completely covered. Place another tortilla in the center of the pan so that the baking sheet is completely covered by tortillas.
Top tortillas with ground beef mixture and sprinkle with cheese, making sure that the meat and cheese goes all the way to the edges of the pan.
Place another tortilla in the center of the pan, on top of the meat and cheese filling. Now fold each tortilla into the center, completely covering all of the meat and cheese filling. Spray top of tortillas with non-stick cooking spray.
Place a second cookie sheet on top of quesadilla (to help it hold it's shape while it bakes).
Cook in preheated oven for 20 minutes, then remove top baking sheet and continue to cook for another 10-15 minutes or until top is golden and crispy
Slice into pieces and serve with desired toppings.