Saute onions in butter and salt for 2-3 minutes over medium heat.
Add the peppers and zucchini and continue to cook for 5 minutes. Set aside.
Pour a few tablespoons of enchilada sauce in a 9x13 baking dish.
Cut the tortillas in half and arrange them in the bottom of the dish (as shown). This is the bottom layer.
Spread half of the vegetable mixture over the tortillas.
Spread half of the shredded beef over the veggies.
Evenly spread about half of the jar of sauce over the beef and vegetable layer.
Top with half of the package of Mexican cheese.
Repeat the layers: veggies, beef, sauce, and cheese.
Bake uncovered at 375 degrees Fahrenheit for 20 minutes.
Finish by broiling for 2 minutes to brown the cheese.
Let sit for 5 minutes before serving.
For the healthiest version of this recipe, use high-quality, organic ingredients.