1Heat oven to 350°F. Lightly spray 3-quart casserole with cooking spray.
2In 12-inch nonstick skillet, heat oil over medium heat. Add bell pepper, onion, garlic and salt; cook 5 minutes, stirring occasionally, until vegetables are soft. Stir in cumin; cook 1 minute. Stir in flour; cook 3 minutes. Reduce heat to low. Add broth and sour cream; cook 5 minutes, stirring frequently. Add chicken; stir to blend. Remove from heat.
3Place tortillas between damp microwavable paper towels. Microwave in batches on High 30 seconds to soften. Arrange 4 tortillas in casserole. Top with one-third of the chicken mixture (about 2 cups); sprinkle with 1 cup of the cheese. Repeat layers twice.
4Bake uncovered 35 to 45 minutes or until bubbly and browned.