Preheat oven to 400 degrees. Coat an 8-inch 2-quart deep-sided casserole with cooking spray. Warm oil over medium heat in large nonstick frying pan. Add onions and garlic, stirring frequently for 3 minutes, until tender. Add carrots and cook for 2 minutes. Stir in beans, tomatoes, tomato sauce, peppers and chili powder and bring to a boil. Lower heat and cook 5 minutes, until slightly thick. Save 1/4 cup and set aside. Place one tortilla in bottom of casserole dish. Top with half of vegetable mixture and 1/3 cup of cheddar. Add second tortilla, rest of vegetable mixture and 1/3 cup of cheddar. Top with third tortilla and 1/4 cup of saved vegetables. Sprinkle with green onions and the remaining 1/3 cup of cheese. Bake 15 to 20 minutes. Let it stand out of oven 5 minutes. Cut into wedges.