Let the black beans soak for about 8 hours (do not reuse the soaking water, as it is full of starch, which makes the beans indigestible). Bring to a boil and simmer for about 1 hour and 30 minutes, or until the beans are tender. Add water as needed during cooking.
Pour a little oil into a skillet and sauté 1 red onion, 1 red bell pepper, and the black beans, adding cumin and garlic powder to taste. Pour in a little water, mix well, and reduce the heat to low.
Mash the avocados and add the other red onion, jalapeño peppers, lime juice, and lime zest. Season with salt.
Take each tortilla and add the cheese, black beans, and vegetables to one half. Spread guacamole on the other half. Fold the tortilla in half.
Pour a little oil into a large nonstick skillet. Place the tortillas side by side, two at a time. Cook until the underside is browned. Then turn and brown the other side. Repeat until all the tortillas are browned.
Serve with store-bought salsa, sour cream, and cilantro, if desired.
