1. Preheat oven to 425 degrees. Lightly oil a 9-inch pie pan or coat it with nonstick spray.
2. In a medium bowl, combine beans, avocado, 1/2 cup scallions and salsa. Season with salt and pepper.
3. Spread 3 tablespoons enchilada sauce over bottom of prepared pan. Place 1 tortilla over sauce. Spread tortilla with 1/4 cup bean mixture and sprinkle with 1 tablespoon cheese. Continue layering sauce, tortillas, bean mixture and cheese, ending with a tortilla. Spread top with remaining sauce and sprinkle with remaining cheese and 2 tablespoons scallions.
4. Lightly oil a sheet of foil or coat it with nonstick spray. Place foil, oiled-side down, over tortilla stack. Bake for 20 to 25 minutes, or until heated through. Cut into 4 wedges and serve, passing yogurt separately.