Preheat oven to 350 degrees. Combine frozen bell peppers and frozen corn in a non-stick skillet and saute (with no oil) on medium heat. Add a healthy serving of taco seasoning and salt to taste. Cook for 10-15 minutes until the peppers are heated through.
Heat the 2 cans tomato sauce, diced tomatoes with chiles, cumin, oregano and garlic powder in a large pot. Add a dash of cayenne if you like things spicy. Once heated through, blend with an immersion blender, and add broth until the sauce is the consistency you like. (For a thinner sauce, add more broth).
Heat up refried black beans over medium heat and add taco seasoning to taste. Warm corn tortillas in the microwave (wrap in a paper towel, heat for 40-60 seconds until warmed through).
Now it's time for assembly! In a large casserole dish, begin creating the enchiladas: Take a corn tortilla, spread refried black beans down the middle (about 3-4 Tbsp), top with veggie mixture, top with 1-2 Tbsp vegan cheese (if using), roll.
Once all the enchiladas are rolled up in the dish, top with the enchilada sauce and the remaining vegan cheese (if using).
Bake, covered with foil at 350 degrees for 10-12 min. Remove foil, heat for another 7-9 min (if using vegan cheese, bake until vegan cheese is melted and bubbly).