Peel, rinse, and chop onion. Peel and mince garlic.
Wipe any soil off mushrooms with a damp paper towel. Cut into thin slices.
Rinse bell pepper. Remove core and seeds. Cut into thin strips.
Rinse spinach. Tear or chop into pieces.
Rinse and peel sweet potato. Shred using the large holes of a box grater.
Grate white cheddar cheese.
Tear tortillas in half.
In a large skillet over medium-low heat, heat oil. Add onions. Cook until transparent, about 5-7 minutes. Add garlic, mushrooms, bell pepper, and oregano. Raise heat to high. Stir in shredded sweet potato. Cook until soft, about 8-10 minutes more. Stir in spinach. Cover and cook until just wilted, about 2 minutes.
In a medium bowl, crumble Queso Fresco or Feta. Add grated white cheddar. Stir to mix cheeses.
Spray the bottom of a 9-by-13-inch baking dish with non-stick spray. Layer 9 tortilla halves over the bottom, with the flat edges against the side of the dish and the rounded pieces overlapping in the center. Cover the tortillas with ½ of the cooked vegetables. Drizzle ½ of the enchilada sauce on top. Sprinkle ½ of the cheese. Layer the remaining 9 tortilla halves over the cheese. Add another layer using the remaining vegetables, sauce, and cheese.
Cover baking dish with aluminum foil.
Bake for 40 minutes. Remove foil. Keep baking until cheese on top is lightly browned, about 10 minutes more.
Chef’s Notes
For more heat, add ½ teaspoon red pepper flakes or a pinch cayenne pepper when cooking the veggies.
Use leftover cooked veggies like green beans, carrots, eggplants, winter squash, or greens. Cut veggies into small pieces. Warm in a skillet or microwave before adding to the lasagna.
To ensure this recipe is truly gluten-free, use ingredients labeled "certified gluten-free." Some foods, like oats or soy sauce, can contain traces of gluten depending on the brand or processing methods.