In a large skillet, heat the 2 tablespoons of olive oil over medium heat. Add in the tomato paste and sauté for about 2 minutes, allowing it to caramelize slightly. Sprinkle in the 1/4 cup of all-purpose flour, stirring constantly to create a roux. Gradually whisk in the 3 cups of vegetable broth until the mixture is smooth. Season with 2 teaspoons of ground cumin, 1/2 teaspoon of garlic powder, 1/2 teaspoon of onion powder, and 1/4 teaspoon of chili powder. Bring to a simmer, allowing the sauce to thicken. Taste and adjust seasoning with salt and pepper as needed.
In a large mixing bowl, combine the rinsed and drained black beans, 1 1/2 cups of sweet corn, fresh baby spinach, sliced green onions, chopped cilantro, and an additional 2 teaspoons of ground cumin. Gently fold in the vegan cheese shreds or nutritional yeast, mixing well to combine all the ingredients.
Preheat your oven to 375°F (190°C). Spread a thin layer of the prepared sauce on the bottom of a 9x13 inch baking dish. Take a tortilla and spoon about 1/4 cup of the filling into the center. Roll the tortilla tightly around the filling and place it seam-side down in the baking dish. Repeat this process with the remaining tortillas and filling.
Once all the enchiladas are in the baking dish, pour the remaining sauce over the top, ensuring each enchilada is generously coated. For a cheesy finish, top with additional vegan cheese shreds if desired.
Cover the baking dish with aluminum foil and bake in the preheated oven for 20 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the enchiladas are bubbly and lightly golden on top.