This is looks like a lot of work but it actually comes together very quickly,  Dr.C.

For the Base:

• 3 medium sweet potatoes, diced                                         
• 1/2 large onion, diced
• 1 red pepper, diced                                                             
• 3 garlic cloves, minced
• 1 15-ounce can black beans, rinsed and drained                 
• 1 lime, juiced
• 2 green onions, sliced
• 1/2 teaspoon chili powder                                                    
• 1/2 teaspoon cumin
• 1 bag spinach, chopped                                                        
• A handful cilantro, chopped
• 3 cups  cheese, (vegan if preferred) shredded                       
• 12-15 corn tortillas

For the Sauce:

• 3 tablespoons olive oil                                                         
• 1/4 cup flour 1/4 cup tomato paste                                        
• 2 tablespoons cumin                     
• 1 tablespoon chili powder                                                    
• 1/2 teaspoon garlic powder    
• 1/2 teaspoon onion powder                                                   
• 4 cups vegetable broth

To Make the Enchilada Sauce:

1. Heat the olive oil.Add all spices and toast them for about 1 minute.
2. Whisk in the tomato paste.
3. Finally, whisk in the flour. It will form a ball. Let cook for about 1 more minute.
4. Slowly add the broth, whisking as you add it, until you get a smooth consistency.
5. Bring sauce to a boil until it thickens. Set it aside.

To Make the Base:

1. Preheat oven to 375°F.
2. Toss the sweet potatoes in olive oil, salt, and pepper and place them on a baking sheet.
3. Roast them for 20-25 minutes.
4. In a large pan, sauté the onion and pepper in a little bit of olive oil until they’re soft.
5. Add the garlic, 1/2 teaspoon chili powder, and cumin.
6. Cook this for about 2 more minutes.
7. Add in the spinach and cook it until just wilted.
8. Remove this from the heat and place the mixture in a bowl
9. Add the black beans, green onion, lime juice, and cilantro.
10. Mix this well.
11. When sweet potatoes are done, add them to this mixture as well and mix it to combine.
12. Assemble the lasagna in a 9×13 pan.
13. Cut each corn tortilla in half.
14. Add 1 cup of sauce to the pan and move it around to cover the bottom.
15. Place the flat side of the tortillas in the pan so they are flush with the sides of the pan, essentially creating a rectangle with 2 tortillas.
16. Cover the bottom with tortillas.
17. Add 1/2 of the sweet potato mixture, 1 cup of cheese, and 1 more cup of enchilada sauce.
18. Start the layer again with corn tortillas, the rest of the sweet potato mixture, cheese, and sauce.
19. Finish the dish with a layer of tortillas, cover with the rest of the sauce, and top with the rest of the cheese.
20. Bake lasagna for 20 minutes, then broil the top until golden brown.
21. Let it sit for 10 minutes before cutting.

This is from one of my fave sites One Green Planet