Add all sauce ingredients to medium saucepan and heat over medium high heat. Bring to a simmer, reduce heat to low and let simmer for 10 minutes.
Filling
Add chopped onion, 1 minced garlic clove and about 2 tablespoons of water to a large skillet and saute for 2 minutes over medium heat.
Add peppers, corn, black beans and leafy greens, stir, reduce heat to low, and let cook for 3 minutes. Remove from heat.
Assembly
Coat a 9x13" casserole dish with oil. Place 6 tortilla shells on the bottom of the dish. Spread approximately 2 cups of filling over shell and top with approximately half a cup of sauce.
Repeat this process with all tortilla shells (4 layers of tortillas), reserving about 2 tablespoons of sauce to spread across the top shells.
After spreading remaining sauce over the top shells, sprinkle with minced jalapeno and fresh cilantro (if using).
Bake on middle shelf of oven for 40 minutes. Remove from oven, sprinkle with nutritional yeast (optional) and let sit for 10-15 minutes before serving.
Notes
Letting dish sit after cooking allows it to firm up and makes for easy cutting and serving. This dish freezes well. Simply pack in a freezer safe container and heat when ready to enjoy.