Preheat the oven to 400 degrees F. Set aside a 9×13-inch (ungreased) baking dish.
In a large saucepan, combine the vegetable broth, onion, tomato sauce, chili powder, oregano, and salt. Bring the mixture to a low simmer and cook, stirring occasionally, for 4 to 5 minutes. Whisk in the black bean flour and cook, stirring constantly, for 1 minute. Add the pinto beans and hot sauce, and cook another 1-2 minutes. Remove from the heat.
Ladle 1/4 of the sauce into the baking dish, evenly covering the bottom of the dish. Layer 3 tortillas and 1/2 cup of the cheese on top of the sauce. (I like to cut 2 of the tortillas in half, and 1 of them in sixths in order to create a layer that doesn’t overlap.) Repeat the layering process three more times–sauce, tortillas, and cheese. (Not ending with a sauce layer allows the top layer of tortillas to become crisp, which is my favorite part.)
Bake the enchiladas, uncovered, for approximately 20 minutes or until a little bubbly around the edges. Remove from the oven.
Sprinkle with any of the desired toppings and pass salsa and sour cream at the table, if desired. For leftover enchiladas, lightly cover with foil and reheat in a 350 degree F oven for 20 minutes or until hot throughout.
