Heat oven to 350°F. Spray 9-inch glass pie plate or 9 1/2-inch glass deep-dish pie plate with cooking spray. In 12-inch skillet or 4-quart Dutch oven, cook beef and onion over medium-high heat, stirring occasionally, until thoroughly cooked; drain. Stir in bell pepper, corn, taco seasoning mix, tomatoes and enchilada sauce. Heat to boiling; remove from heat.
Spread about 1/4 of beef mixture in thin layer in pie plate. Top with 3 tortillas (tortillas will overlap), 1/4 of beef mixture and 1/3 of cheese. Repeat layers 2 more times, starting with tortillas and ending with cheese on top. Pie plate will be very full but should not overflow.
Bake about 30 minutes or until cheese is melted and lightly browned. Let stand 5 minutes before serving. Top each serving with sour cream and green onions.