Sauce

Heat olive oil in a medium pot over medium-high heat. Add onions and garlic. Cook and stir until onions begin to soften, about 2 minutes. Stir in tomato sauce, broth, chili powder, cumin, oregano and salt. Mix well. Bring mixture to a boil. Reduce heat to low and simmer, uncovered, for 5 minutes. Remove sauce from heat and stir in cilantro. Preheat oven to 375 F. Spray a deep, 9 x 13-inch casserole dish with cooking spray or lightly oil. Spoon about ¾ cup sauce over bottom of dish. Top with 3 tortillas, cutting as necessary to make them fit. Top tortillas with another ¾ cup sauce followed by 1/3 chicken, 1/3 beans, 1/3 squash and ¼ cheese. Repeat layering two more times: ¾ cup sauce, 1/3 chicken, 1/3 beans, 1/3 squash and ¼ cheese. Top with remaining 3 tortillas, followed by remaining sauce and cheese. Spray foil with cooking spray (or lightly oil) and cover casserole dish. Bake in preheated oven for 40 minutes. Uncover and bake for another 10 minutes. Let casserole stand, uncovered, for 10 minutes before serving. Serve hot with any or all of the optional garnishes.