Preheat oven to 350°F. Coat 9 x 13-inch baking dish with non-stick cooking spray. Heat oil in large skillet over medium heat. Add onion. Sauté until tender. Add 1 can enchilada sauce. Simmer 5 minutes. Combine chicken and black beans in medium bowl. Add onion and sauce mixture. Combine Cheddar and mozzarella in another bowl. Add ½ cup cheese to chicken mixture. Toss to combine. Place 2 tortillas on microwave-safe plate. Cover with plastic wrap. Microwave on high 20 seconds, or until warm. Place 1 tortilla in baking dish. Spoon ¼ cup chicken mixture into tortilla. Roll up tortilla. Place seam side down in baking dish. Repeat with remaining warm tortilla. Repeat with 7 more batches of 2 tortillas each. Pour remaining can of sauce over enchiladas. Top with remaining cheese mixture. Bake, uncovered, for 30 minutes, or until sauce is bubbly and cheese is melted and golden brown. Garnish with chopped cilantro. Serves 6–8.